Related CoreCLR work #50938 (the attribute was added as part of #50954).

The slightly interesting thing for Mono is that we'll need to call down to reflection.c to clear to the unmanaged hash tables that map unmanaged metadata method representations to their managed counterparts.

Also need to clear the Cache in RuntimeType added by #78840

Enable the tests in #50954

Part of #44806 Part of #57365