Changes proposed in this pull request

This is a minor update to #1604.

• fix several raw strings that lead to syntax warnings in Python 3.12
• add Python 3.12 post-merge test as recommended by @bryanwweber (note that the runner is currently still failing due to upstream limitations, see https://github.com/Cantera/cantera/actions/runs/6061035003/job/16445794850)
• force system libraries in ubuntu docker post-merge-test
• add hdf5 to fedora docker post-merge-test

At this point, fedora rawhide is still the only runner that uses Python 3.12 successfully.

Checklist

• The pull request includes a clear description of this code change
• Commit messages have short titles and reference relevant issues
• Build passes (scons build & scons test) and unit tests address code coverage
• Style & formatting of contributed code follows contributing guidelines
• The pull request is ready for review