Add support for Python 3.13

[rmartin16]

Changes

• Add Python 3.13.0
• Bump 3.12.5 -> 3.12.7

PR Checklist:

• All new features have been tested
• All new features have been documented
• I have read the CONTRIBUTING.md file
• I will abide by the code of conduct

[rmartin16]

I had forgotten that Python.NET isn't ready for Python 3.13 yet. Additionally, there is some added complexity here on Windows for the stub binary. Feel free to close and address separately if necessary.

[freakboy3742]

Toga doesn't support Python 3.13 on Windows, but pygame and console apps clearly work; excluding Toga from the CI matrix until this is resolved seems the right approach.

I'll tag a new stub binary right after merging this.

[rmartin16]

Awesome; I'll do the same now for PySide6 for Flatpak.