Python 3.12 version support and make tests tolerate the presence of OpenMP for system Python

[ogrisel]

Fixes #146.

Actually our CI does not need any update to test against the latest Python version available on conda-forge.

This PR is mostly about updating pyproject.toml and renaming VERSION_PYTHON to PYTHON_VERSION to sound more correct English.

EDIT: also tolerate the presence of OpenMP when Python is not installed via conda.

[ogrisel]

BTW I confirm that the pylatest_conda_forge build already uses Python 3.12 and test_command_line_empty passes on that environment contrary to what is reported on a gentoo env in #146.

[ogrisel]

@jeremiedbb this PR is good to go. It should speed-up the conda install of other PRs because the default solver is really really slow for some reason.

[jeremiedbb]

LGTM. We could also stop assuming that none of the libraries of interest are linked to python itself and just remove this test, don't you think ?

[ogrisel]

We could also stop assuming that none of the libraries of interest are linked to python itself and just remove this test, don't you think ?

I think we can merge this PR as it is for now and remove this test if this happens gain in another case.

Still, it's interesting to discover that our assumptions about Python runtime dependencies were wrong (in some cases). This might be important to inform us about choices about packaging such native libraries, see for instance numpy/numpy#24857.