Updates to python test packages

[tornaria]

Testing the changes

• I tested the changes in this PR: briefly

Mostly taken from #44160, this updates several packages used for testing:

• python3-coverage: update to 7.2.7.
• python3-flaky: update to 3.7.0.
• python3-hypothesis: update to 6.76.0.
• python3-mock: update to 5.0.2.
• python3-pytest-asyncio: update to 0.21.0.
• python3-pytest-cov: update to 4.1.0.
• python3-pytest-mock: update to 3.10.0.
• python3-pytest-xdist: enable tests.
• python3-testpath: update to 0.6.0.

There are also 3 new packages:

• python3-process-tests-2.1.2, needed to check pytest-cov
• python3-pytest-console-scripts-1.4.1, need to check jupyter_server
• python3-pytest-trio-0.8.0, need to check pytest-asyncio

[tornaria]

Force push: disabled two tests in python3-pytest-asyncio which fail on CI (due to binding to a tcp address).

[tornaria]

Major changes from previous version:

• changelog entries are replaced by the direct link
• explicitly depend on python3-setuptools, not just via python3-wheel
• python3-pytest-trio no longer needs a venv for testing (uses the trick from python3-ipython: update to 8.14.0. #44268, i.e., set PYTHONPATH=.)
• python3-coverage and python3-pytest-cov still test in a venv; if using PYTHONPATH some tests will fail

@ahesford comments welcome