[Local GC] Move some EE-specific finalize-on-unload logic out of the GC (dotnet/corec...

[Local GC] Move some EE-specific finalize-on-unload logic out of the GC (dotnet/coreclr#10598)

* Move some EE-specific logic to a callback on GCToEEInterface

* Fix the sample

* Consistent style for pointers

* Code review feedback: Move app domain index check into EE callback and make ShouldFinalizeObjectForUnload always return true (due to CoreCLR not having app domains)

* Code review feedback: Fix a comment and add a TODO for bringing these changes to desktop

Commit migrated from https://github.com/dotnet/coreclr/commit/41617fee235d22d9e6dc1fa31548de63637551fa