In PYTHON-4520 we made the async tests run by default like this:

    python -m pytest -v --capture=tee-sys --durations=5 --maxfail=10 $TEST_ARGS
    python -m pytest -v --capture=tee-sys --durations=5 --maxfail=10 test/asynchronous/ $TEST_ARGS

There are two problems with this approach:

1. Running pytest twice produces 2 independent XML and coverage files, where the second one overwrites the first.
2. In test suites where we pass a python file via TEST_ARGS, the suite gets run twice, first on it's own and then a second time with test/asynchronous.