Use mock from the stdlib. (#9772)

changelog.d/9772.misc

setup.cfg

setup.py

synmark/suites/logging.py

tests/api/test_auth.py

tests/app/test_openid_listener.py

tests/appservice/test_appservice.py

tests/appservice/test_scheduler.py

tests/crypto/test_keyring.py

tests/events/test_presence_router.py

tests/federation/test_complexity.py

tests/federation/test_federation_catch_up.py

tests/federation/test_federation_sender.py

tests/handlers/test_admin.py

tests/handlers/test_appservice.py

tests/handlers/test_auth.py

tests/handlers/test_cas.py

tests/handlers/test_directory.py

tests/handlers/test_e2e_keys.py

tests/handlers/test_e2e_room_keys.py