Build Wheels with ABI3

[ocefpaf]

This PR builds a single wheel for each platform using Python 3.11 ABI3. That means we drop support for 3.10 and 3.9, I can try to re-add 3.10 later but I don't think 3.9 is worth it. I would stick with SPEC 0 though, that way we can remove 3.10 now and make our lives a bit easier.

Note that, with ABI3, we don't need to rebuild the extension every new Python release. I just tested this wheel against 3.14 and it works as expected.

Closes #626

[CLAassistant]

All committers have signed the CLA.

[ocefpaf]

I don't know how tox works to fix the failures here, but a py310_abl3 wheel is built and tested against py314.

[ocefpaf]

I cannot figure out what is wrong with the CIs. In a different env, where the wheels are built and tested, everything passes. I'm guessing it is the lockfiles, maybe the cython version there is different?

[trexfeathers]

Regarding Tox: we've been worried about it for a while, since tox-conda is unsupported and out-of-date. Unfortunately it has now stopped working. We've been meaning to adopt Pixi anyway so I've spent this afternoon writing a PR for that:

#636

Hopefully I can get that merged soon and then we can update your PR.