CI: Upgrade to ubuntu-24.04, install Python free threading from conda-forge

[mroeschke]

No description provided.

[datapythonista]

Seems like that the python-freethreading from conda-forge is not recognized as a valid Python, no idea why. But other than that this looks great, much cleaner.

[lithomas1]

Probably needs a bump of meson/meson-python.

[lithomas1]

Looks like that did it.
Thanks for the PR!

(last failure looks like a compiler warning)

[lithomas1]

submitted cython/cython#6870 for the warning.

[lithomas1]

thanks @mroeschke

[lumberbot-app]

Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

git checkout 2.3.x
git pull

2. Cherry pick the first parent branch of the this PR on top of the older branch:

git cherry-pick -x -m1 b2b2d04e419e44932d51017ececb5c3a86b15925

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

git commit -am 'Backport PR #61410: CI: Upgrade to ubuntu-24.04, install Python free threading from conda-forge'

4. Push to a named branch:

git push YOURFORK 2.3.x:auto-backport-of-pr-61410-on-2.3.x

5. Create a PR against branch 2.3.x, I would have named this PR:

"Backport PR #61410 on branch 2.3.x (CI: Upgrade to ubuntu-24.04, install Python free threading from conda-forge)"

And apply the correct labels and milestones.

Congratulations — you did some good work! Hopefully your backport PR will be tested by the continuous integration and merged soon!

Remember to remove the Still Needs Manual Backport label once the PR gets merged.

If these instructions are inaccurate, feel free to suggest an improvement.

[mroeschke]

The free threading stuff isn't on 2.3 so no need for backport