add support for free-threaded wheels

[ngoldbaum]

See this actions run on my fork.

Let me know if using setup-python on MacOS is problematic for some reason.

Fixes #913.

[alex]

I believe we intentionally wanted to build against python.org Python's, but I absolutely do not remember why. Do you @reaperhulk ?

[ngoldbaum]

Maybe related to the note about MacOS here and the difference in behavior on Python < 3.11?

I'd need to figure out how to trigger a free-threaded install using the installer, but happy to switch it back if that was a load-bearing choice :)

[reaperhulk]

Probably macOS SDK compatibility, although I don’t recall if there was another reason.

[ngoldbaum]

I couldn't figure out a way to include the necessary plist file into the actions workflow definition directly, so I added actions/checkout to the MacOS wheel builder workflow and chose to store the plist file in the bcrypt repo, alongside the github actions configuration. Let me know if that's problematic.

[ngoldbaum]

All the plist manipulation is cribbed from @colesbury's PR adding free-threading support to actions/python-versions: https://github.com/actions/python-versions/pull/319/files

[ngoldbaum]

I think the test failure is unrelated

[ngoldbaum]

I think is ready for another pass

[alex]

Sorry I missed this before. THanks!

[alex]

Ooops, sorry should have caught this before: can you this to .github/config/macos-pkg-choices-freethreaded.xml (i.e. not in workflows)?