Update Python from 3.11 to 3.12.

[JamesAmrhein]

Rather than go directly to 3.13, we've only upgraded to 3.12 because TomS needs that version for his memory testing updates.
FermiPy team was also made aware of this change. Our build tests include their internal tests.

[JamesAmrhein]

Code changes completed.
GitHub Actions built all packages Linux/MacOS amd64/arm64 w/o error. Uploaded with dev tag.
Internal testing passed w/o error.
FermiPy testing passed w/o error.
Hasn't been tested in FermiBottle yet.
Leaving as "in process" until further testing can be completed.