SIL: Add verification of open_existential_addr instructions
SIL: Add verification of open_existential_addr instructions

Make sure that all uses of "immutable_access" instructions are not mutating the
opened value.

Only enable verification if we have COW existentials enabled.

jmgc/swift,austinzheng/swift,benlangmuir/swift,jckarter/swift,gregomni/swift,jmgc/swift,OscarSwanros/swift,apple/swift,lorentey/swift,devincoughlin/swift,djwbrown/swift,harlanhaskins/swift,atrick/swift,rudkx/swift,amraboelela/swift,glessard/swift,gribozavr/swift,hooman/swift,frootloops/swift,airspeedswift/swift,lorentey/swift,aschwaighofer/swift,parkera/swift,codestergit/swift,ahoppen/swift,jtbandes/swift,gribozavr/swift,return/swift,nathawes/swift,brentdax/swift,harlanhaskins/swift,shahmishal/swift,devincoughlin/swift,djwbrown/swift,benlangmuir/swift,manavgabhawala/swift,karwa/swift,jtbandes/swift,stephentyrone/swift,manavgabhawala/swift,tkremenek/swift,apple/swift,shahmishal/swift,airspeedswift/swift,swiftix/swift,stephentyrone/swift,natecook1000/swift,zisko/swift,gregomni/swift,OscarSwanros/swift,xedin/swift,apple/swift,huonw/swift,zisko/swift,zisko/swift,milseman/swift,return/swift,harlanhaskins/swift,lorentey/swift,zisko/swift,manavgabhawala/swift,hooman/swift,Jnosh/swift,alblue/swift,swiftix/swift,hooman/swift,tkremenek/swift,shajrawi/swift,felix91gr/swift,Jnosh/swift,gregomni/swift,nathawes/swift,zisko/swift,karwa/swift,jtbandes/swift,danielmartin/swift,felix91gr/swift,swiftix/swift,tkremenek/swift,xwu/swift,felix91gr/swift,uasys/swift,gribozavr/swift,jmgc/swift,harlanhaskins/swift,shahmishal/swift,allevato/swift,bitjammer/swift,roambotics/swift,danielmartin/swift,devincoughlin/swift,sschiau/swift,gribozavr/swift,xedin/swift,roambotics/swift,practicalswift/swift,karwa/swift,arvedviehweger/swift,codestergit/swift,manavgabhawala/swift,JGiola/swift,codestergit/swift,devincoughlin/swift,shajrawi/swift,stephentyrone/swift,felix91gr/swift,parkera/swift,shajrawi/swift,practicalswift/swift,roambotics/swift,jmgc/swift,uasys/swift,bitjammer/swift,danielmartin/swift,sschiau/swift,nathawes/swift,practicalswift/swift,allevato/swift,jopamer/swift,tinysun212/swift-windows,glessard/swift,danielmartin/swift,Jnosh/swift,deyton/swift,roambotics/swift,return/swift,tinysun212/swift-windows,tinysun212/swift-windows,rudkx/swift,glessard/swift,swiftix/swift,sschiau/swift,lorentey/swift,bitjammer/swift,devincoughlin/swift,gregomni/swift,atrick/swift,frootloops/swift,jtbandes/swift,parkera/swift,calebd/swift,milseman/swift,OscarSwanros/swift,CodaFi/swift,deyton/swift,austinzheng/swift,calebd/swift,shajrawi/swift,shajrawi/swift,jckarter/swift,djwbrown/swift,uasys/swift,xwu/swift,devincoughlin/swift,return/swift,calebd/swift,uasys/swift,felix91gr/swift,deyton/swift,atrick/swift,glessard/swift,aschwaighofer/swift,jopamer/swift,deyton/swift,nathawes/swift,brentdax/swift,jmgc/swift,parkera/swift,JGiola/swift,ahoppen/swift,hooman/swift,apple/swift,rudkx/swift,huonw/swift,karwa/swift,return/swift,sschiau/swift,jmgc/swift,shajrawi/swift,tjw/swift,jtbandes/swift,amraboelela/swift,apple/swift,practicalswift/swift,karwa/swift,atrick/swift,aschwaighofer/swift,jckarter/swift,tkremenek/swift,parkera/swift,xedin/swift,xwu/swift,shajrawi/swift,glessard/swift,airspeedswift/swift,karwa/swift,huonw/swift,alblue/swift,natecook1000/swift,tinysun212/swift-windows,benlangmuir/swift,xedin/swift,OscarSwanros/swift,milseman/swift,djwbrown/swift,benlangmuir/swift,brentdax/swift,xwu/swift,tinysun212/swift-windows,allevato/swift,hughbe/swift,nathawes/swift,airspeedswift/swift,bitjammer/swift,uasys/swift,gregomni/swift,arvedviehweger/swift,alblue/swift,zisko/swift,Jnosh/swift,airspeedswift/swift,felix91gr/swift,danielmartin/swift,brentdax/swift,devincoughlin/swift,parkera/swift,aschwaighofer/swift,tjw/swift,frootloops/swift,CodaFi/swift,rudkx/swift,CodaFi/swift,alblue/swift,manavgabhawala/swift,swiftix/swift,OscarSwanros/swift,ahoppen/swift,harlanhaskins/swift,Jnosh/swift,danielmartin/swift,arvedviehweger/swift,Jnosh/swift,xwu/swift,jopamer/swift,rudkx/swift,natecook1000/swift,karwa/swift,roambotics/swift,uasys/swift,frootloops/swift,shajrawi/swift,sschiau/swift,hooman/swift,sschiau/swift,allevato/swift,jckarter/swift,karwa/swift,austinzheng/swift,natecook1000/swift,devincoughlin/swift,uasys/swift,brentdax/swift,JGiola/swift,amraboelela/swift,airspeedswift/swift,jckarter/swift,practicalswift/swift,huonw/swift,codestergit/swift,deyton/swift,tinysun212/swift-windows,return/swift,milseman/swift,nathawes/swift,tinysun212/swift-windows,hughbe/swift,jopamer/swift,gribozavr/swift,tjw/swift,huonw/swift,calebd/swift,benlangmuir/swift,ahoppen/swift,jmgc/swift,alblue/swift,jckarter/swift,OscarSwanros/swift,codestergit/swift,lorentey/swift,xedin/swift,lorentey/swift,practicalswift/swift,alblue/swift,xedin/swift,CodaFi/swift,jckarter/swift,practicalswift/swift,amraboelela/swift,milseman/swift,hooman/swift,atrick/swift,manavgabhawala/swift,gregomni/swift,OscarSwanros/swift,stephentyrone/swift,amraboelela/swift,calebd/swift,gribozavr/swift,codestergit/swift,apple/swift,roambotics/swift,hughbe/swift,tjw/swift,bitjammer/swift,calebd/swift,arvedviehweger/swift,deyton/swift,tkremenek/swift,bitjammer/swift,Jnosh/swift,ahoppen/swift,shahmishal/swift,manavgabhawala/swift,shahmishal/swift,alblue/swift,xedin/swift,CodaFi/swift,shahmishal/swift,danielmartin/swift,CodaFi/swift,calebd/swift,stephentyrone/swift,arvedviehweger/swift,austinzheng/swift,airspeedswift/swift,huonw/swift,allevato/swift,jopamer/swift,gribozavr/swift,tjw/swift,hughbe/swift,jopamer/swift,stephentyrone/swift,natecook1000/swift,aschwaighofer/swift,frootloops/swift,swiftix/swift,ahoppen/swift,return/swift,parkera/swift,deyton/swift,jtbandes/swift,harlanhaskins/swift,practicalswift/swift,lorentey/swift,rudkx/swift,frootloops/swift,atrick/swift,codestergit/swift,bitjammer/swift,zisko/swift,tjw/swift,xwu/swift,lorentey/swift,tkremenek/swift,shahmishal/swift,aschwaighofer/swift,CodaFi/swift,djwbrown/swift,brentdax/swift,hughbe/swift,austinzheng/swift,milseman/swift,gribozavr/swift,brentdax/swift,allevato/swift,huonw/swift,JGiola/swift,harlanhaskins/swift,milseman/swift,jopamer/swift,felix91gr/swift,djwbrown/swift,xwu/swift,amraboelela/swift,stephentyrone/swift,nathawes/swift,JGiola/swift,tkremenek/swift,swiftix/swift,hughbe/swift,natecook1000/swift,arvedviehweger/swift,natecook1000/swift,sschiau/swift,hooman/swift,parkera/swift,amraboelela/swift,hughbe/swift,glessard/swift,tjw/swift,sschiau/swift,benlangmuir/swift,arvedviehweger/swift,frootloops/swift,austinzheng/swift,allevato/swift,jtbandes/swift,xedin/swift,aschwaighofer/swift,JGiola/swift,austinzheng/swift,shahmishal/swift,djwbrown/swift