Add pytest options for faster local testing

The celery.inspect.().active() broadcast used in the cleanup of fixture worker waits until timeout (default 1 s) is reached, which accumulates for each test with this fixture, e.g. about 14 min instead of 7 min on a laptop. Removal may lead to tasks still running during the next test.

This MR adds the pytest option --celery-inspect-timeout, which can be used to decrease the timeout for faster local testing.

It further adds the option --fixture-filters to run only tests that depend (directly or indirectly) on a list of fixtures and do not depend on fixtures prefixed with '!'.