dotnet-pgo used in build with new packages without ensuring matching framework

[ericstj]

Similar to #106740

Discovered in #106873 (comment)

ILCompiler projects are referencing a package version of System.Reflection.Metdata and copying that to the output and running it during the build, without ensuring that the runtime they are running against supports that version of the package.

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[MichalStrehovsky]

I've deleted the S.R.Metadata package reference in ILCompiler.TypeSystem in #107343.

dotnet-pgo still doesn't work because it depends on ILCompiler.Reflection.ReadyToRun and that one does need a S.R.Metadata package reference because it's netstandard2.0 for ILSpy sake. If we could make it $(NetCoreAppToolCurrent), the problem would go away but that would break ILSpy. I don't know enough nuget-fu to resolve this. Reopening and moving to crossgen2 area path since this is not in a component shared with nativeaot anymore.