Remove Python 3.9 support and the legacy retworkx import

[IvanIsCoding]

In short, this PR:

• Moves the build from 3.9 ABI to 3.10 ABI
• Removes Python 3.9 from GitHub actions
• Bumps Python in CI: 3.10->3.12 to avoid having to do bumps when 3.10 reaches EoL
• Removes the legacy retworkx shim
• Run tests with the Python 3.14 RC. I will add a release note for 3.14 once it's formally released and we are closer to the 0.18.0 release

[coveralls]

Pull Request Test Coverage Report for Build 19056599075

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 94.175%

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Totals
Change from base Build 19053565245:	0.0%
Covered Lines:	18268
Relevant Lines:	19398

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💛 - Coveralls

[IvanIsCoding]

I bumped ruff to lint for Python 3.10 and it found some fixes that are only available for 3.10+.

[mtreinish]

I'm fine with this, I know we had previously discussed stopping retworkx releases in 1.0, but I think it's been long enough. Just a few inline questions. The only open question really is if we want to add 3.14 to the package metadata and test matrix in this PR or do it separately.

[IvanIsCoding]

I will address the comments on Saturday. I plan to add 3.14 support on a separate PR.

It will need some minor change for the MyPy stub tests. Right now, we are using a version that is pinned and might not support 3.14. At least I am confident there are no pre-compiled binaries for it (although MyPy ships a Python-only version)

[IvanIsCoding]

Also, I just remembered we need to bump cibuildwheel’s version to support testing with 3.14. So after we merge this (it’s ready), I will kick off the 3.14 support PR separately and its test builds