CPython 3.14 and Cython==3.1.0 CI issues

[jakkdl]

Tracking issue for the skipifs & pinning added in #3264

• [BUG] Cython 3.1.0 fails to compile basic async program with linetrace=True: __pyx_CoroutineObject has no member named __pyx_pymonitoring_state cython/cython#6865 Cython==3.1.0 broke line tracing/code coverage on async code. Fixed on master, so we're only waiting for a new release. The version is pinned in tox.ini and ci.yml
• segfault in gc with 3.14.0b1, trio and pytest python/cpython#133932 broke test_run.test_error_in_run_loop which is marked with a skipif
• Jedi, mypy, pyright & pylint all have incomplete support for 3.14 so test_static_tool_sees_all_symbols and test_static_tool_sees_class_members are marked with skipif.
  • we could start adding tool-specific logic once they start supporting 3.14, but these aren't critical tests to run on every version imo
• Python 3.14.0-beta.1 C-extension builds try to link against python314t.lib on non-threaded python python/cpython#133779 windows+cffi+3.14 is completely broken and the run doesn't start at all, so continue-on-error has been enabled for windows 3.14. Should be fixed in beta 2.
• [3.14] change in behaviour in gc.get_referrers(some_local) python/cpython#125603 see Python 3.14: test_ki_protection_doesnt_leave_cyclic_garbage fails #3209

[A5rocks]

The next 3.14 beta is 5/27 so we will be able to check the last checkbox then.

[jakkdl]

the segfault also looks to be fixed by beta 2, it's been fixed on main/ and got a backport PR python/cpython#134494