Fix and re-enable some finalizer tests (dotnet/coreclr#22771)

Fix and re-enable some finalizer tests (dotnet/coreclr#22771)

Mark key allocating methods noinline, otherwise they may get inlined
under jit stress and leave jit temps referring to allocations that the test
expects should be collectible.

Resolves dotnet/coreclr#19218.

Commit migrated from https://github.com/dotnet/coreclr/commit/268a6b777febf10e97badede96dcddd54b54c4e1