Avoid box allocation in Encoding.EncodingName (#6142)
Avoid box allocation in Encoding.EncodingName (#6142)

`Encoding.EncodingName` concatenates a `string` with an `int` via
`string.Concat(object, object)`, which results in the `int` being
boxed.

This change avoids the box by calling `int.ToString()`,
allowing `string.Concat(string, string)` to be used.
ruben-ayrapetyan/coreclr,parjong/coreclr,krytarowski/coreclr,hseok-oh/coreclr,rartemev/coreclr,mskvortsov/coreclr,Dmitry-Me/coreclr,JosephTremoulet/coreclr,wateret/coreclr,russellhadley/coreclr,vinnyrom/coreclr,vinnyrom/coreclr,dasMulli/coreclr,KrzysztofCwalina/coreclr,dasMulli/coreclr,hseok-oh/coreclr,russellhadley/coreclr,Dmitry-Me/coreclr,yeaicc/coreclr,yeaicc/coreclr,russellhadley/coreclr,mmitche/coreclr,parjong/coreclr,gkhanna79/coreclr,cshung/coreclr,yeaicc/coreclr,AlexGhiondea/coreclr,ramarag/coreclr,martinwoodward/coreclr,yeaicc/coreclr,dasMulli/coreclr,ramarag/coreclr,dasMulli/coreclr,ZhichengZhu/coreclr,bartdesmet/coreclr,yizhang82/coreclr,kyulee1/coreclr,mmitche/coreclr,James-Ko/coreclr,ZhichengZhu/coreclr,vinnyrom/coreclr,bartdesmet/coreclr,jhendrixMSFT/coreclr,russellhadley/coreclr,rartemev/coreclr,KrzysztofCwalina/coreclr,manu-silicon/coreclr,botaberg/coreclr,JosephTremoulet/coreclr,qiudesong/coreclr,dasMulli/coreclr,wateret/coreclr,sjsinju/coreclr,James-Ko/coreclr,jhendrixMSFT/coreclr,sagood/coreclr,gkhanna79/coreclr,mskvortsov/coreclr,Dmitry-Me/coreclr,sagood/coreclr,russellhadley/coreclr,qiudesong/coreclr,hseok-oh/coreclr,JonHanna/coreclr,cmckinsey/coreclr,qiudesong/coreclr,cmckinsey/coreclr,tijoytom/coreclr,pgavlin/coreclr,gkhanna79/coreclr,wtgodbe/coreclr,ragmani/coreclr,mskvortsov/coreclr,vinnyrom/coreclr,AlexGhiondea/coreclr,JonHanna/coreclr,rartemev/coreclr,cydhaselton/coreclr,vinnyrom/coreclr,jhendrixMSFT/coreclr,James-Ko/coreclr,sagood/coreclr,martinwoodward/coreclr,manu-silicon/coreclr,ruben-ayrapetyan/coreclr,cydhaselton/coreclr,neurospeech/coreclr,jamesqo/coreclr,mskvortsov/coreclr,gkhanna79/coreclr,krk/coreclr,ramarag/coreclr,ragmani/coreclr,YongseopKim/coreclr,naamunds/coreclr,cydhaselton/coreclr,sagood/coreclr,parjong/coreclr,hseok-oh/coreclr,mskvortsov/coreclr,jhendrixMSFT/coreclr,gkhanna79/coreclr,JosephTremoulet/coreclr,yizhang82/coreclr,yizhang82/coreclr,martinwoodward/coreclr,krytarowski/coreclr,ruben-ayrapetyan/coreclr,pgavlin/coreclr,manu-silicon/coreclr,neurospeech/coreclr,cydhaselton/coreclr,ruben-ayrapetyan/coreclr,russellhadley/coreclr,bartdesmet/coreclr,cmckinsey/coreclr,parjong/coreclr,pgavlin/coreclr,hseok-oh/coreclr,botaberg/coreclr,shahid-pk/coreclr,krytarowski/coreclr,gkhanna79/coreclr,KrzysztofCwalina/coreclr,vinnyrom/coreclr,dpodder/coreclr,bartdesmet/coreclr,naamunds/coreclr,JonHanna/coreclr,alexperovich/coreclr,wtgodbe/coreclr,parjong/coreclr,sjsinju/coreclr,krytarowski/coreclr,alexperovich/coreclr,poizan42/coreclr,neurospeech/coreclr,cshung/coreclr,alexperovich/coreclr,wateret/coreclr,ragmani/coreclr,Dmitry-Me/coreclr,yeaicc/coreclr,botaberg/coreclr,mmitche/coreclr,YongseopKim/coreclr,KrzysztofCwalina/coreclr,bartdesmet/coreclr,neurospeech/coreclr,ramarag/coreclr,parjong/coreclr,James-Ko/coreclr,krk/coreclr,jamesqo/coreclr,YongseopKim/coreclr,wateret/coreclr,yizhang82/coreclr,alexperovich/coreclr,JosephTremoulet/coreclr,cshung/coreclr,cmckinsey/coreclr,shahid-pk/coreclr,poizan42/coreclr,JonHanna/coreclr,mskvortsov/coreclr,botaberg/coreclr,kyulee1/coreclr,krytarowski/coreclr,AlexGhiondea/coreclr,vinnyrom/coreclr,tijoytom/coreclr,ragmani/coreclr,James-Ko/coreclr,ragmani/coreclr,ruben-ayrapetyan/coreclr,ragmani/coreclr,sjsinju/coreclr,shahid-pk/coreclr,pgavlin/coreclr,manu-silicon/coreclr,AlexGhiondea/coreclr,krk/coreclr,wtgodbe/coreclr,KrzysztofCwalina/coreclr,rartemev/coreclr,kyulee1/coreclr,alexperovich/coreclr,sjsinju/coreclr,tijoytom/coreclr,cmckinsey/coreclr,AlexGhiondea/coreclr,martinwoodward/coreclr,JonHanna/coreclr,JonHanna/coreclr,ZhichengZhu/coreclr,mmitche/coreclr,qiudesong/coreclr,qiudesong/coreclr,martinwoodward/coreclr,manu-silicon/coreclr,jhendrixMSFT/coreclr,AlexGhiondea/coreclr,krytarowski/coreclr,kyulee1/coreclr,jamesqo/coreclr,tijoytom/coreclr,rartemev/coreclr,rartemev/coreclr,YongseopKim/coreclr,YongseopKim/coreclr,yeaicc/coreclr,ZhichengZhu/coreclr,qiudesong/coreclr,poizan42/coreclr,dasMulli/coreclr,jamesqo/coreclr,botaberg/coreclr,cshung/coreclr,JosephTremoulet/coreclr,KrzysztofCwalina/coreclr,KrzysztofCwalina/coreclr,poizan42/coreclr,krk/coreclr,bartdesmet/coreclr,botaberg/coreclr,ramarag/coreclr,poizan42/coreclr,shahid-pk/coreclr,Dmitry-Me/coreclr,wtgodbe/coreclr,pgavlin/coreclr,cydhaselton/coreclr,hseok-oh/coreclr,manu-silicon/coreclr,naamunds/coreclr,mmitche/coreclr,neurospeech/coreclr,jamesqo/coreclr,James-Ko/coreclr,bartdesmet/coreclr,wtgodbe/coreclr,tijoytom/coreclr,dpodder/coreclr,tijoytom/coreclr,neurospeech/coreclr,naamunds/coreclr,manu-silicon/coreclr,dpodder/coreclr,jhendrixMSFT/coreclr,shahid-pk/coreclr,sjsinju/coreclr,ZhichengZhu/coreclr,naamunds/coreclr,naamunds/coreclr,dpodder/coreclr,sjsinju/coreclr,cmckinsey/coreclr,sagood/coreclr,kyulee1/coreclr,ruben-ayrapetyan/coreclr,kyulee1/coreclr,shahid-pk/coreclr,wateret/coreclr,wtgodbe/coreclr,pgavlin/coreclr,ZhichengZhu/coreclr,yeaicc/coreclr,cshung/coreclr,martinwoodward/coreclr,JosephTremoulet/coreclr,jhendrixMSFT/coreclr,ramarag/coreclr,yizhang82/coreclr,cshung/coreclr,jam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