Fix support for older python versions

[baszoetekouw]

This PR replaces #869 It retains the changes needed to support older python versions.

Also, it makes some changes to the CI, notably:

• re-enable the pylint tests, as this catch some more stuff than ruff on its own. I can remove this part, if you prefer
• run the tests for all upstream-supported versions of python (3.8+)
• split out the tests in separate GA steps, and reduce verbosity, so that it's easier to spot which tests fail.

As a side note: because coverage now is checked in the CI, it might make sense to enable a tool like https://codecov.io/, which provides a nice web interface showing where coverage is missing, and also adds an automatic CI check to check that new PRs don't decrease coverage.

[p12tic]

In Fix python>3.11 compatibility what was mean is probably `Fix python<3.11 compatibility.

Split out the different tests in separate CI steps ... commit message is too long, should be max 72 characters. Now it overflows.

[p12tic]

Overall looks good. I stand corrected, can bring back pylint.

[baszoetekouw]

Thanks for the feedback! This should fix the outstanding issues.

[p12tic]

Match editorconfig max line length with ruff config should be part of add editorconfig. Aside from that, all is good. Thanks!

[baszoetekouw]

done!