[3.12] gh-121084: Fix test_typing random leaks (GH-121360) (#121372)

gh-121084: Fix test_typing random leaks (GH-121360)

Clear typing ABC caches when running tests for refleaks (-R option):
call _abc_caches_clear() on typing abstract classes and their
subclasses.
(cherry picked from commit 5f660e8e2ca3acfb89ccbdd990f072149b6baa6a)

Co-authored-by: Victor Stinner <vstinner@python.org>