Use Coreclr transport packages (#37163)
Use Coreclr transport packages (#37163)

* Replace CoreCLR package with transport package

This allows us to remove the manual download step

* Remove IL and NI folders, use IL in debug or when specified

I also simplified some of these targets.   NuGet automatically includes all files in native,
so additional inclusion was unnecessary.

* Disable IL CoreLib swap for UAP10.0.16299 and AOT

ericstj/corefx,shimingsg/corefx,shimingsg/corefx,shimingsg/corefx,BrennanConroy/corefx,wtgodbe/corefx,wtgodbe/corefx,wtgodbe/corefx,ViktorHofer/corefx,ViktorHofer/corefx,ViktorHofer/corefx,BrennanConroy/corefx,wtgodbe/corefx,wtgodbe/corefx,shimingsg/corefx,ericstj/corefx,wtgodbe/corefx,shimingsg/corefx,ericstj/corefx,ViktorHofer/corefx,shimingsg/corefx,ViktorHofer/corefx,shimingsg/corefx,ericstj/corefx,ericstj/corefx,ViktorHofer/corefx,ericstj/corefx,ViktorHofer/corefx,ericstj/corefx,wtgodbe/corefx,BrennanConroy/corefx