Tracking of Python 3.11 compatibility

[C4ptainCrunch]

Python 3.11 tests are failing since a few hours, this is due to a legit bug in Python and is tracked on pytest-dev/pytest#10008 and python/cpython#93359. This should be fixed with the next pre-release of Python.

This issue also keep track of the stable release that is currently targeted for 2022-10-03. At that time, we should:

• Change the build matrix to disallow 3.11 tests to fail
• Enforce 3.11 tests in the branch protection
• Add 3.12 in the tests (as experimental) ?
• Update PyPi classifiers
• Build with 3.11 on ReadThe Docs (.readthedocs.yaml)
• Build tox targets docs and checks on 3.11

Edit:

• check PyPy for new releases
• update mypy target python_version
• update the pinned version of mypy and check for new breakages
  (we should do that semi-regularly and this might actually be a good point in time for that, see also Pin mypy to a specific version to avoid breakages of main in the future #329)

[C4ptainCrunch]

They released a new version of Python quite quickly : https://twitter.com/pyblogsal/status/1532043180631375879
I re-ran the test and it's all green again 🎉

[N-Coder]

We might also want to include these steps in general as a "Updating for a newly-released python version" section in the docs. As a refence we can also take the changes made in #301 and #338. I'd also include:

• check PyPy for new releases
• update mypy target python_version
• update the pinned version of mypy and check for new breakages
  (we should do that semi-regularly and this might actually be a good point in time for that, see also Pin mypy to a specific version to avoid breakages of main in the future #329)

[N-Coder]

And also for deprecating old versions:

• update pyproject.toml and tox.ini
• update --py37-plus for pyupgrade in .pre-commit-config.yaml
• check for compatibility imports, e.g. cached_property, stuff from typing, importlib_resources,...

[C4ptainCrunch]

Update: we are almost there. We are only missing 3.12 experimental tests and maybe PyPy and mypy (but that can be done later)
I'm also considering releasing 0.8.0dev1 with the changes