PyPy3.11 and CPython 3.14/3.14t support

[fohrloop]

Closes: #414
Closes: #481

Add CI tests for PyPy3.11, CPython 3.14 and CPython 3.14 free-threaded

[fohrloop]

The pipelines are failing

1) Free-threaded "3.14t" python not found

See the pipelines outcome here. The errors were:

Seems that were still using old actions/setup-python (5.1) version at few places.

2) Test coverage on ubuntu-latest 3.14

See here. Uncovered lines:

Name                                  Stmts   Miss Branch BrPart  Cover   Missing
---------------------------------------------------------------------------------
src/wakepy/dbus_adapters/jeepney.py      27      0      4      1    97%   21->24
---------------------------------------------------------------------------------
TOTAL                                  1352      0    298      1    99%

Debugging

• It's not missing jeepney. If uninstalling jeepney and running the tests, getting 37% test coverage on ubuntu.

[fohrloop]

Got the error on python3.14t (and 3.14) reproduced locally. The "test coverage issue" looks like this:

So this was not a line coverage but a branch coverage issue. I don't know why coveragepy would assume that there's a branch here in the class definition. The problem was fixed by adding a docstring to the class.