[3.10] bpo-45097: Add more tests for shutdown_asyncgens() (GH-28154) (GH-28159)

* bpo-45097: Add more tests for shutdown_asyncgens() (GH-28154)
(cherry picked from commit c2970fdec52788b6d9ff419ab7e31f255d87433d)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
1 file changed