Add support for Python 3.14

[dkropachev]

Add Python 3.14 to supported list and start testing it.

Pre-review checklist

• I have split my patch into logically separate commits.
• All commit messages clearly explain what they change and why.
• I added relevant tests for new features and bug fixes.
• All commits compile, pass static checks and pass test.
• PR description sums up the changes and reasons why they should be introduced.
• I have provided docstrings for the public items that I want to introduce.
• I have adjusted the documentation in ./docs/source/.
• I added appropriate Fixes: annotations to PR description.

[dkropachev]

Just to keep updated, by some reason instead of asincio and libev it uses twisted which uses zope, which does not support python 3.14 and fails by this reason.

[fruch]

@dkropachev what's holding this one out of the door ?

[fruch]

@dkropachev how about adding 3.14t ? into testing only

[dkropachev]

@fruch , lets fix ongling cicd problem first

[dkropachev]

@fruch , @Lorak-mmk , after all issues were sorted out in separate PRs this one looks so much cleaner, please take a look.

[dkropachev]

@Lorak-mmk , can you please review it

[Lorak-mmk]

LGTM if CI passes

[fruch]

• pp311-manylinux_x86_64 wheel failed - can we ditch pypy builds in general ?
• windows 3.14t - greenlet_msvc_compat.hpp(70): error C3861: '_PyCode_GetTLBCArray': identifier not found

I would suggest taking 3.14t to a followup PR

[dkropachev]

• pp311-manylinux_x86_64 wheel failed - can we ditch pypy builds in general ?
• windows 3.14t - greenlet_msvc_compat.hpp(70): error C3861: '_PyCode_GetTLBCArray': identifier not found

I would suggest taking 3.14t to a followup PR

Done, created an issue on that - #599