Python 3.13 wheels

[remia]

Here is a list of changes included:

• Bumping cibuildwheel, we should have working macOS ARM testing
• Bumping the default pybind11 version used in the build (no strong reason but seems like a good time)
• Adding Python 3.13 wheels and removing 3.7 wheels
• Fixing macOS build issues related to the deployment target and recent updates in cibuildwheel
• FIxing Windows test issues related to DLL search directory, the exact cause has not been identified but the workflow should now complete successfully. Debugging was made harder as I haven't been able to get any print out of the OpenColorTestSuite.py, even after increasing build-verbosity to 3 in cibuildwheel (warnings worked though). Use of dlltracer (stdout or stderr or audit events) didn't yield any results, but might if the debug print issue is fixed (though it probably depends on when the segfault is triggered exactly).

Tagging @KelSolaar

[KelSolaar]

LGTM besides the classifier.

[remia]

Nice work! Really strange, that the OCIO_PYTHON_LOAD_DLLS_FROM_PATH thing is causing problems. That's pretty baffling.

Do we want to support free-threaded mode too for Python 3.13?

For the segfault, let's continue the discussion in https://github.com/AcademySoftwareFoundation/OpenColorIO/issues/2040!

I don't think we have the resources to add support for GIL-free Python in the coming release and not exactly sure yet what work will be required to be honest. From a quick look, I assume we have to upgrade to pybind 2.13 and start using py::mod_gil_not_used() to check whether we need to handle unlocking / locking the GIL or not?