Update dependencies, run tests on Python 3.11/12

[lkubb]

• Updates pip-tools to 6.14 (last version to support Python 3.7) and pip to 23.3.1 (latest one, for 3.12).
• Runs tests on Python 3.11 and 3.12, drops 3.5 and 3.6 from compile target tests (3.6 still works though, 3.5 fails now because the specified backports.zoneinfo version is not available).
• Passes --no-header to pip-compile since this header now includes the Python version it was compiled with (the actual one, not the overridden one). This might be unwanted, not sure.
• Converts attrs usage to dataclasses.

Please excuse me submitting this out of the blue. For context, I investigated possible updates to the salt-extension templates yesterday and got a bit hung up with the requirements specifics. It seems since the creation of setuptools-declarative-requirements, setuptools has learned to read requirements files via setup.cfg/pyproject.toml (v62.6), so has pip-compile (v6.1.0).

This should tackle the first step in deprecating the usage of setuptools-declarative-requirements, the next one would be for this tool to learn how to request extras from pip-compile and to make it aware of the files specified in pyproject.toml (if any are, otherwise just pass through the requested extra). That's beyond my understanding of the templating needs and my current time budget though.

If unwanted, I hope this at least saves you some time in the future. :)

(I have not updated the poetry.lock file since I'm not sure whether I should do this in my own environment).