Python 3.13 testing and other revisions to the CI suite

[joaander]

Description

Test freud with Python 3.13 and make other modernization changes to the CI scripts.

Motivation and Context

Ensure that freud functions with the latest versions Python and all dependencies.

Unfortunately, both MDAnalysis and Numba releases are lagging. We will need to re-enable these optional test dependencies at a future date. I will not chain the delay a freud release to an optional dependency.

How Has This Been Tested?

CI checks.

Checklist:

• [x] I have read the CONTRIBUTING document.
• [x] My code follows the code style of this project.
• [ ] I have updated the documentation (if relevant).
• [ ] I have added tests that cover my changes (if relevant).
• [x] All new and existing tests passed.
• [x] I have updated the credits.
• [x] I have updated the Changelog.