Delete COMPlus_FinalizeOnShutdown (dotnet/coreclr#23595)

Delete COMPlus_FinalizeOnShutdown (dotnet/coreclr#23595)

This compat quirk is increasingly more broken since the framework is generally not compatible with, and we have not heard anybody actually using it.

Changed Environment.HasShutdownStarted to unconditionally return false. It does not make sense for it to ever return true with shutdown finalization disabled.

Commit migrated from https://github.com/dotnet/coreclr/commit/8913aaa1388e263d537b19e78caaed6b124fc0ea