Change null constant type to be TYP_REF for isinst nullcheck expansion
Change null constant type to be TYP_REF for isinst nullcheck expansion

In the importer when inlining the fast expansion sequence for
isinst/castclass, the code was typing the constant 0 source of the
compare with TYP_I_IMPL instead of TYP_REF. Not only does this create
an inconsistently typed compare but it causes value-numbering of
the same constants with different types to not be equal. This blocks
later assertion propagation that propagates null-checks and prevents
many cases from being eliminated.

This change changes the type of the constant gtNode to be TYP_REF.
With this change there are many good diffs in the frameworks and
other assemblies.

Ran testing in desktop branch including SuperPMI asm diffs. Asm
diffs show hundreds of methods with improvements in framework
, Roslyn, and other internal assemblies. 1% code size reduction in
the methods that have changes. All diffs are elimination of redundant
null-checks.

dpodder/coreclr,sejongoh/coreclr,perfectphase/coreclr,misterzik/coreclr,Alcaro/coreclr,botaberg/coreclr,krytarowski/coreclr,botaberg/coreclr,Alcaro/coreclr,ganeshran/coreclr,misterzik/coreclr,cydhaselton/coreclr,Lucrecious/coreclr,neurospeech/coreclr,Sridhar-MS/coreclr,GuilhermeSa/coreclr,yizhang82/coreclr,blackdwarf/coreclr,rartemev/coreclr,Lucrecious/coreclr,stormleoxia/coreclr,sperling/coreclr,cmckinsey/coreclr,josteink/coreclr,KrzysztofCwalina/coreclr,sagood/coreclr,KrzysztofCwalina/coreclr,shahid-pk/coreclr,jhendrixMSFT/coreclr,richardlford/coreclr,richardlford/coreclr,sagood/coreclr,xoofx/coreclr,JonHanna/coreclr,Lucrecious/coreclr,Alcaro/coreclr,AlfredoMS/coreclr,ZhichengZhu/coreclr,Dmitry-Me/coreclr,kyulee1/coreclr,dasMulli/coreclr,wkchoy74/coreclr,schellap/coreclr,Godin/coreclr,Alcaro/coreclr,wkchoy74/coreclr,orthoxerox/coreclr,AlfredoMS/coreclr,bartdesmet/coreclr,dkorolev/coreclr,orthoxerox/coreclr,hanu412/coreclr,Lucrecious/coreclr,bartdesmet/coreclr,tijoytom/coreclr,LLITCHEV/coreclr,grokys/coreclr,ruben-ayrapetyan/coreclr,bjjones/coreclr,perfectphase/coreclr,apanda/coreclr,ganeshran/coreclr,Godin/coreclr,iamjasonp/coreclr,Godin/coreclr,dkorolev/coreclr,manu-silicon/coreclr,James-Ko/coreclr,chenxizhang/coreclr,sergey-raevskiy/coreclr,grokys/coreclr,vinnyrom/coreclr,ericeil/coreclr,dasMulli/coreclr,apanda/coreclr,yeaicc/coreclr,shana/coreclr,mokchhya/coreclr,misterzik/coreclr,GuilhermeSa/coreclr,AlfredoMS/coreclr,misterzik/coreclr,AlexGhiondea/coreclr,JosephTremoulet/coreclr,ragmani/coreclr,jakesays/coreclr,apanda/coreclr,cydhaselton/coreclr,GuilhermeSa/coreclr,JosephTremoulet/coreclr,dasMulli/coreclr,ktos/coreclr,fernando-rodriguez/coreclr,roncain/coreclr,mocsy/coreclr,chenxizhang/coreclr,Djuffin/coreclr,alexperovich/coreclr,sergey-raevskiy/coreclr,chrishaly/coreclr,LLITCHEV/coreclr,manu-silicon/coreclr,rartemev/coreclr,YongseopKim/coreclr,KrzysztofCwalina/coreclr,martinwoodward/coreclr,lzcj4/coreclr,stormleoxia/coreclr,MCGPPeters/coreclr,libengu/coreclr,krk/coreclr,krixalis/coreclr,ragmani/coreclr,cydhaselton/coreclr,gitchomik/coreclr,DickvdBrink/coreclr,chrishaly/coreclr,perfectphase/coreclr,neurospeech/coreclr,James-Ko/coreclr,benpye/coreclr,mmitche/coreclr,ytechie/coreclr,iamjasonp/coreclr,ericeil/coreclr,JonHanna/coreclr,bjjones/coreclr,cmckinsey/coreclr,shahid-pk/coreclr,cshung/coreclr,Lucrecious/coreclr,schellap/coreclr,krytarowski/coreclr,russellhadley/coreclr,grokys/coreclr,manu-silicon/coreclr,yeaicc/coreclr,perfectphase/coreclr,LLITCHEV/coreclr,chrishaly/coreclr,Sridhar-MS/coreclr,wtgodbe/coreclr,mmitche/coreclr,dkorolev/coreclr,DasAllFolks/coreclr,SlavaRa/coreclr,qiudesong/coreclr,SlavaRa/coreclr,grokys/coreclr,naamunds/coreclr,hanu412/coreclr,gitchomik/coreclr,spoiledsport/coreclr,benpye/coreclr,vinnyrom/coreclr,krytarowski/coreclr,hanu412/coreclr,SpotLabsNET/coreclr,xoofx/coreclr,cshung/coreclr,chaos7theory/coreclr,chuck-mitchell/coreclr,spoiledsport/coreclr,russellhadley/coreclr,yizhang82/coreclr,ramarag/coreclr,AlfredoMS/coreclr,jhendrixMSFT/coreclr,DickvdBrink/coreclr,hanu412/coreclr,geertdoornbos/coreclr,sjsinju/coreclr,stormleoxia/coreclr,jakesays/coreclr,xtypebee/coreclr,SlavaRa/coreclr,naamunds/coreclr,blackdwarf/coreclr,alexperovich/coreclr,bartonjs/coreclr,stormleoxia/coreclr,fernando-rodriguez/coreclr,dkorolev/coreclr,naamunds/coreclr,mskvortsov/coreclr,krixalis/coreclr,swgillespie/coreclr,gitchomik/coreclr,pgavlin/coreclr,matthubin/coreclr,ramarag/coreclr,dasMulli/coreclr,wateret/coreclr,wkchoy74/coreclr,cydhaselton/coreclr,jhendrixMSFT/coreclr,krk/coreclr,wkchoy74/coreclr,cmckinsey/coreclr,krixalis/coreclr,josteink/coreclr,swgillespie/coreclr,OryJuVog/coreclr,taylorjonl/coreclr,ZhichengZhu/coreclr,matthubin/coreclr,mocsy/coreclr,benpye/coreclr,ruben-ayrapetyan/coreclr,mskvortsov/coreclr,cmckinsey/coreclr,qiudesong/coreclr,gkhanna79/coreclr,roncain/coreclr,chaos7theory/coreclr,hseok-oh/coreclr,GuilhermeSa/coreclr,zmaruo/coreclr,ragmani/coreclr,bartdesmet/coreclr,mokchhya/coreclr,taylorjonl/coreclr,richardlford/coreclr,jakesays/coreclr,vinnyrom/coreclr,jamesqo/coreclr,schellap/coreclr,ramarag/coreclr,shahid-pk/coreclr,geertdoornbos/coreclr,Alcaro/coreclr,rartemev/coreclr,apanda/coreclr,bjjones/coreclr,Lucrecious/coreclr,roncain/coreclr,fffej/coreclr,ytechie/coreclr,wkchoy74/coreclr,Godin/coreclr,roncain/coreclr,ganeshran/coreclr,fffej/coreclr,naamunds/coreclr,ericeil/coreclr,JonHanna/coreclr,russellhadley/coreclr,yizhang82/coreclr,alexperovich/coreclr,gkhanna79/coreclr,fieryorc/coreclr,jamesqo/coreclr,xoofx/coreclr,ragmani/coreclr,iamjasonp/coreclr,mocsy/coreclr,jhendrixMSFT/coreclr,vinnyrom/coreclr,DasAllFolks/coreclr,rartemev/coreclr,ktos/coreclr,vinnyrom/coreclr,kyulee1/coreclr,mokchhya/coreclr,wateret/coreclr,Djuffin/coreclr,lzcj4/coreclr,gkhanna79/coreclr,cshung/coreclr,dkorolev/coreclr,taylorjonl/coreclr,Sridhar-MS/coreclr,mskvortsov/coreclr,hseok-oh/coreclr,sergey-raevskiy/coreclr,dpodder/coreclr,blackdwarf/coreclr,zmaruo/coreclr,schellap/coreclr,perfectphase/coreclr,grokys/coreclr,serenabenny/coreclr,yizhang82/coreclr,josteink/coreclr,libengu/coreclr,sjsinju/coreclr,sjsinju/coreclr,swgillespie/coreclr,ramarag/coreclr,qiudesong/coreclr,fernando-rodriguez/coreclr,blackdwarf/coreclr,Dmitry-Me/coreclr,hanu412/coreclr,DickvdBrink/coreclr,shahid-pk/coreclr,lzcj4/coreclr,david-mitchell/coreclr,jamesqo/coreclr,OryJuVog/coreclr,fieryorc/coreclr,ZhichengZhu/coreclr,apanda/coreclr,James-Ko/coreclr,perfectphase/coreclr,benpye/coreclr,Djuffin/coreclr,mskvortsov/coreclr,shana/coreclr,andschwa/coreclr,mocsy/coreclr,JonHanna/coreclr,sperling/coreclr,matthubin/coreclr,AlfredoMS/coreclr,Godin/coreclr,manu-silicon/coreclr,chrishaly/coreclr,geertdoornbos/coreclr,dkorolev/coreclr,pgavlin/coreclr,xoofx/coreclr,schellap/coreclr,mokchhya/coreclr,DasAllFolks/coreclr,andschwa/coreclr,chaos7theory/coreclr,sejongoh/coreclr,ruben-ayrapetyan/coreclr,GuilhermeSa/coreclr,richardlford/coreclr,kyulee1/coreclr,Dmitry-Me/coreclr,tijoytom/coreclr,martinwoodward/coreclr,bartdesmet/coreclr,MCGPPeters/coreclr,swgillespie/coreclr,chuck-mitchell/coreclr,wateret/coreclr,mokchhya/coreclr,YongseopKim/coreclr,iamjasonp/coreclr,blackdwarf/coreclr,Godin/coreclr,AlexGhiondea/coreclr,pgavlin/coreclr,xtypebee/coreclr,mskvortsov/coreclr,serenabenny/coreclr,JosephTremoulet/coreclr,cmckinsey/coreclr,bitcrazed/coreclr,YongseopKim/coreclr,lzcj4/coreclr,hseok-oh/coreclr,wkchoy74/coreclr,AlexGhiondea/coreclr,ruben-ayrapetyan/coreclr,taylorjonl/coreclr,josteink/coreclr,gitchomik/coreclr,david-mitchell/coreclr,poizan42/coreclr,taylorjonl/coreclr,gkhanna79/coreclr,wateret/coreclr,krk/coreclr,schellap/coreclr,krytarowski/coreclr,poizan42/coreclr,schellap/coreclr,alexperovich/coreclr,James-Ko/coreclr,Djuffin/coreclr,ericeil/coreclr,spoiledsport/coreclr,LLITCHEV/coreclr,krytarowski/coreclr,jakesays/coreclr,sergey-raevskiy/coreclr,david-mitchell/coreclr,xtypebee/coreclr,MCGPPeters/coreclr,orthoxerox/coreclr,chenxizhang/coreclr,dpodder/coreclr,ZhichengZhu/coreclr,DasAllFolks/coreclr,shahid-pk/coreclr,josteink/coreclr,ramarag/coreclr,bartdesmet/coreclr,tijoytom/coreclr,ramarag/coreclr,Godin/coreclr,ZhichengZhu/coreclr,sergey-raevskiy/coreclr,bartonjs/coreclr,taylorjonl/coreclr,mokchhya/coreclr,swgillespie/coreclr,ZhichengZhu/coreclr,James-Ko/coreclr,ragmani/coreclr,pgavlin/coreclr,josteink/coreclr,kyulee1/coreclr,Djuffin/coreclr,rartemev/coreclr,yizhang82/coreclr,botaberg/coreclr,KrzysztofCwalina/coreclr,yizhang82/coreclr,stormleoxia/coreclr,ktos/coreclr,Djuffin/coreclr,LLITCHEV/coreclr,dasMulli/coreclr,chuck-mitchell/coreclr,spoiledsport/coreclr,ktos/coreclr,qiudesong/coreclr,libengu/coreclr,qiudesong/coreclr,cmckinsey/coreclr,KrzysztofCwalina/coreclr,lzcj4/coreclr,spoiledsport/coreclr,grokys/coreclr,iamjasonp/coreclr,krixalis/coreclr,sjsinju/coreclr,apanda/coreclr,sperling/coreclr,naamunds/coreclr,matthubin/coreclr,Sridhar-MS/coreclr,ruben-ayrapetyan/coreclr,krytarowski/coreclr,kyulee1/coreclr,krk/coreclr,andschwa/coreclr,OryJuVog/coreclr,jamesqo/coreclr,DickvdBrink/coreclr,krixalis/coreclr,ktos/coreclr,gkhanna79/coreclr,fernando-rodriguez/coreclr,sperling/coreclr,bartonjs/coreclr,cydhaselton/coreclr,chrishaly/coreclr,Samana/coreclr,bartdesmet/coreclr,iamjasonp/coreclr,xoofx/coreclr,sejongoh/coreclr,tijoytom/coreclr,sperling/coreclr,cshung/coreclr,SlavaRa/coreclr,orthoxerox/coreclr,sagood/coreclr,richardlford/coreclr,geertdoornbos/coreclr,geertdoornbos/coreclr,vinnyrom/coreclr,sagood/coreclr,YongseopKim/coreclr,bjjones/coreclr,sjsinju/coreclr,sejongoh/coreclr,OryJuVog/coreclr,wtgodbe/coreclr,Sridhar-MS/coreclr,SpotLabsNET/coreclr,Samana/coreclr,ganeshran/coreclr,spoiledsport/coreclr,russellhadley/coreclr,ktos/coreclr,russellhadley/coreclr,chenxizhang/coreclr,martinwoodward/coreclr,dpodder/coreclr,Samana/coreclr,DickvdBrink/coreclr,JonHanna/coreclr,wtgodbe/coreclr,mmitche/coreclr,shana/coreclr,bitcrazed/coreclr,AlexGhiondea/coreclr,bartonjs/coreclr,roncain/coreclr,bartonjs/coreclr,geertdoornbos/coreclr,gkhanna79/coreclr,ganeshran/coreclr,kyulee1/coreclr,mocsy/coreclr,DasAllFolks/coreclr,SpotLabsNET/coreclr,shana/coreclr,david-mitchell/coreclr,benpye/coreclr,Samana/coreclr,serenabenny/coreclr,bitcrazed/coreclr,chaos7theory/coreclr,qiudesong/coreclr,wateret/coreclr,parjong/coreclr,yeaicc/coreclr,poizan42/coreclr,hseok-oh/coreclr,bjjones/coreclr,bitcrazed/coreclr,Dmitry-Me/coreclr,sagood/coreclr,shana/coreclr,fffej/coreclr,mmitche/coreclr,Dmitry-Me/coreclr,ramarag/coreclr,shahid-pk/coreclr,roncain/coreclr,YongseopKim/coreclr,ytechie/coreclr,roncain/coreclr,poizan42/coreclr,mocsy/coreclr,yeaicc/coreclr,botaberg/coreclr,chuck-mitchell/coreclr,wtgodbe/coreclr,jhendrixMSFT/coreclr,andschwa/coreclr,xtypebee/coreclr,gitchomik/coreclr,fffej/coreclr,sagood/coreclr,mskvortsov/coreclr,bartonjs/coreclr,fernando-rodriguez/coreclr,libengu/coreclr,chrishaly/coreclr,chuck-mitchell/coreclr,swgillespie/coreclr,JosephTremoulet/coreclr,poizan42/coreclr,KrzysztofCwalina/coreclr,naamunds/coreclr,Lucrecious/coreclr,JonHanna/coreclr,chaos7theory/coreclr,sejongoh/coreclr,Dmitry-Me/coreclr,matthubin/coreclr,fieryorc/coreclr,andschwa/coreclr,pgavlin/coreclr,OryJuVog/coreclr,david-mitchell/coreclr,orthoxerox/coreclr,misterzik/coreclr,hseok-oh/coreclr,yeaicc/coreclr,bitcrazed/coreclr,Samana/coreclr,JosephTremoulet/coreclr,swgillespie/coreclr,Alcaro/coreclr,bitcrazed/coreclr,SpotLabsNET/coreclr,shahid-pk/coreclr,fieryorc/coreclr,ytechie/coreclr,GuilhermeSa/coreclr,naamunds/coreclr,benpye/coreclr,jhendrixMSFT/coreclr,fieryorc/coreclr,MCGPPeters/coreclr,geertdoornbos/coreclr,krk/coreclr,sperling/coreclr,martinwoodward/coreclr,neurospeech/coreclr,andschwa/coreclr,krixalis/coreclr,jhendrixMSFT/coreclr,manu-silicon/coreclr,chaos7theory/coreclr,fernando-rodriguez/coreclr,Samana/coreclr,ytechie/coreclr,pgavlin/coreclr,misterzik/coreclr,sperling/coreclr,martinwoodward/coreclr,tijoytom/coreclr,cshung/coreclr,rartemev/coreclr,zmaruo/coreclr,AlexGhiondea/coreclr,parjong/coreclr,MCGPPeters/coreclr,dasMulli/coreclr,jamesqo/coreclr,bartonjs/coreclr,ZhichengZhu/coreclr,tijoytom/coreclr,wateret/coreclr,ganeshran/coreclr,gitchomik/coreclr,martinwoodward/coreclr,libengu/coreclr,jamesqo/coreclr,josteink/coreclr,hanu412/coreclr,wkchoy74/coreclr,fieryorc/coreclr,zmaruo/coreclr,OryJuVog/coreclr,poizan42/coreclr,dasMulli/coreclr,jakesays/coreclr,mmitche/coreclr,ruben-ayrapetyan/coreclr,bjjones/coreclr,xtypebee/coreclr,bartdesmet/coreclr,ytechie/coreclr,fffej/coreclr,david-mitchell/coreclr,chuck-mitchell/coreclr,cydhaselton/coreclr,neurospeech/coreclr,SlavaRa/coreclr,LLITCHEV/coreclr,krk/coreclr,ragmani/coreclr,martinwoodward/coreclr,chenxizhang/coreclr,alexperovich/coreclr,dpodder/coreclr,SpotLabsNET/coreclr,Sridhar-MS/coreclr,botaberg/coreclr,ericeil/coreclr,James-Ko/coreclr,serenabenny/coreclr,hseok-oh/coreclr,xtypebee/coreclr,sjsinju/coreclr,libengu/coreclr,ktos/coreclr,parjong/coreclr,KrzysztofCwalina/coreclr,SpotLabsNET/coreclr,orthoxerox/coreclr,blackdwarf/coreclr,cmckinsey/coreclr,parjong/coreclr,sejongoh/coreclr,manu-silicon/coreclr,mmitche/coreclr,vinnyrom/coreclr,shana/coreclr,chuck-mitchell/coreclr,dpodder/coreclr,DickvdBrink/coreclr,matthubin/coreclr,botaberg/coreclr,DasAllFolks/coreclr,alexperovich/coreclr,manu-silicon/coreclr,JosephTremoulet/coreclr,wtgodbe/coreclr,mokchhya/coreclr,sejongoh/coreclr,zmaruo/coreclr,AlexGhiondea/coreclr,benpye/coreclr,yeaicc/coreclr,andschwa/coreclr,serenabenny/coreclr,Dmitry-Me/coreclr,stormleoxia/coreclr,stormleoxia/coreclr,xoofx/coreclr,chenxizhang/coreclr,neurospeech/coreclr,lzcj4/coreclr,neurospeech/coreclr,wtgodbe/coreclr,mocsy/coreclr,ericeil/coreclr,AlfredoMS/coreclr,sergey-raevskiy/coreclr,serenabenny/coreclr,taylorjonl/coreclr,bitcrazed/coreclr,zmaruo/coreclr,MCGPPeters/coreclr,parjong/coreclr,russellhadley/coreclr,YongseopKim/coreclr,blackdwarf/coreclr,cshung/coreclr,SlavaRa/coreclr,jakesays/coreclr,LLITCHEV/coreclr,richardlford/coreclr,yeaicc/coreclr,parjong/coreclr,fffej/coreclr