Release Python 3.13t (free-threading) wheel

[hawkinsp]

psutil currently only ships an abi3 wheel, which isn't compatible with Python 3.13t free-threading builds. It'd be great to fix that!

[giampaolo]

Not sure how to do this, nor what it means in terms of effort.

E.g. can we release a single .whl which targets all cPython versions >= 3.13? ...Or we're deemed to create multiple .whl files for every python version (3.13, 3.14, 3.15, etc.)?

CC @mayeut and @colesbury in case they want to chime in.

[mayeut]

There's no limited/stable API/ABI for free-threading yet: https://docs.python.org/3/howto/free-threading-extensions.html#limited-c-api-and-stable-abi

The existing abi3 wheel will continue to work on non free-threading builds of python 3.13+.
For the free-threading builds, a wheel per version is required.