CPython 3.13 support (tracker issue)

[neutrinoceros]

This issue is to plan and keep track on the effort to add support for CPython 3.13 .
See PEP 719 for the release schedule.
At the time of opening, version 3.13.0b2 is available, and NumPy is already publishing nightly wheels for it.

Here's the chronological task list to complete before we can declare support for it.

• wait for our core dependencies to publish nightly builds, or be tested
  • numpy
  • matplotlib BLD: Enable building Python 3.13 wheels for nightlies  matplotlib/matplotlib#28293
    • Pillow
    • contourpy
  • unyt TST: switch bleeding-edge CI to CPython 3.13 unyt#507 (not a real requirement: unyt 3.0.3 appear to be compatible already)
  • cmyt TST: weekly tests against Python 3.13 cmyt#178
  • ewah-bool-utils WHL: enable cp313 wheels ewah_bool_utils#108
• TST: weekly tests against Python 3.13 #4958 replaced by TST: add CPython 3.13 to regular test matrix #5021
• pass all tests on ubuntu
• test cp313 wheels builds for all platform in CI (but don't publish them yet)
  • this is helped by MNT: cleanup cibuildwheel configuration and move it to pyproject.toml #4949
  • ... and Bump the actions group in /.github/workflows with 2 updates #4971
  • WHL: enable cp313 wheels #4973
• enable publication to PyPI
  • requires ABI stability, i.e., CPython 3.13.0rc1
  • WHL: enable cp313 wheels #4973
• TST: add CPython 3.13 to regular test matrix #5021

Supporting the experimental free-threading (a.k.a "nogil") build is a non-goal for this issue.
Relevant PRs are to be linked in this message.

[chrishavlin]

updated the checklist above to reflect 5021 replacing 4958.