Adapt for logging lock internal changes in Python3.13

[musicinmybrain]

Fixes #403.

A brief discussion of the approach is in #403 (comment).

Tested with:

$ PYTHONPATH="${PWD}" python3.12 -c 'from billiard.util import get_logger; print(get_logger())'
<Logger multiprocessing (WARNING)>
$ PYTHONPATH="${PWD}" python3.13 -c 'from billiard.util import get_logger; print(get_logger())'
<Logger multiprocessing (WARNING)>

[Nusnus]

Your logic makes perfect sense to me.
PR Changes look clean and on-point.

Approved by me - thank you!

[musicinmybrain]

You’re welcome!