WHL: drop support for EOL CPythons 3.8 and 3.9 and add explicit support for CPython 3.14

[neutrinoceros]

This is a (hopefully temporary) replacement for #372, adding specialized wheels for 3.14, since demand is expected to increase now that it's available, while #372 isn't ready yet and I can't make any promise on the timeline.

[neutrinoceros]

seeing some issues with pytest-cov VS Python 3.14
This plugin is in general unnecessary so I'm trying to ditch it completely instead of wondering how it should be fixed.

[neutrinoceros]

Note that I explicitly disabled cp314t wheels (which are enabled by default in recent versions of cibuildwheel) purely because I didn't want to sneek them into a release accidentally, but I saw no problem building or testing them on a single thread. I'd adivse more thorough testing in multi-threaded contextes should be conducted before enabling them back, unless it is known that there are no potential shared+mutable states in the cython module.