Core, CI: Add Python 3.12 support

[black-sliver]

What is this fixing or adding?

Add/fix Python 3.12 support. and use 3.12 in CI

• Use a pony fork that works with 3.12 (Unit tests there look all good)
• Need to fix Stardew's use of deprecated assertEquals since it's now gone
• Slight change to ModuleUpdate.py because Python 3.12's ensure_pip does not ship pkg_resources anymore and some tests would fail because they import ModuleUpdate without --yes.

Stardew and ModuleUpdate could be cherry-picked if we want to give upstream pony more time.

How was this tested?

• Unit tests
• Generate of one multi
• Upload of one game to an empty WebHost and checked user-content - I did not check for DB "upgrade" since I deleted my local DB recently.

[agilbert1412]

Stardew changes are totally fine.
Other changes look okay, but my expertise is low so I wouldn't put much weight on that approval

[remyjette]

Created a Python 3.12.3 venv in Windows, tested

• Webhost: launching the webhost which didn't work before sending a location, making sure the tracker updated, closing and relaunching the server to validate the load from the savefile. Didn't see any errors in the log, no warnings other than options deprecations
• Generate: Just did a simple clique generate and looked for errors in the log. Didn't see any. Only warnings were again options deprecations.
• Kivy: Ran the launcher, checked the logs for any Kivy errors, didn't see any. Opened the text client, connected to a slot, still didn't see any errors.

[beauxq]

docs/running from source.md has some lines that say "Python 3.12 is currently unsupported"
I don't know if we want to remove them or change them or change them to 3.13
I don't like the idea of having to change more things in more places with every version change, so I think probably remove.

[black-sliver]

I think it is still undecided how we are going to handle this exactly once we drop 3.8, but kivy sometimes being slow to update might be a problem regardless of our plans, so I think the versions should be mentioned explicitly. We had a bunch of people that were on unsupported python versions and didn't know.

My personal preference would be to roughly follow github ubuntu-latest python for the oldest, which changes around the time when the latest Ubuntu LTS gets its point 1 release. And bleeding edge for the newest. I use arch btw. This is hard to put into words if we don't know when our dependencies will update.