[jit] Fix enum->int casts in gsharedvt code. Fixes #21893.
[mcs] null propagating operator and extension methods
[runtime] Fix Process.PrivateMemorySize64 etc. on ios. Fixes #21882.
[mcs] null propagating operator and expressions which cannot be null
[System] Disable failing test
[Cleanup] Removed .jvm.cs files that are no longer used

They were once part of a special Java target profile, but this is no longer used today.
[Cleanup] Removed net_1_1_java*.sources files

They were once part of a special Java target profile, but this is no longer used today.
[Cleanup] Removed net_1_1_java from Makefiles

It was once part of a special Java target profile, but this is no longer used today.
[Cleanup] Removed JavaEE csproj and sln files

They were once part of a special Java target profile, but this is no longer used today.
[Cleanup] Removed files that imported Java namespaces

They were once part of a special Java target profile, but this is no longer used today.
[Cleanup] Removed TARGET_JVM

It was once part of a special Java target profile, but this is no longer used today.