GH-135552: Add tests to check weakref clearing (GH-136304)

These are tests to ensure behaviour introduced by GH-136189 is working as expected.

Co-authored-by: Mikhail Borisov <43937008+fxeqxmulfx@users.noreply.github.com>
Co-authored-by: Kumar Aditya <kumaraditya@python.org>
Co-authored-by: Neil Schemenauer <nas-github@arctrix.com>