ci: Add Python 3.13 to the test matrix

[cpswan]

Python 3.13 has been released as stable

- What I did

Added 3.13 to the test matrix

- How to verify it

CI

- Description for the changelog

ci: Add Python 3.13 to the test matrix

[cpswan]

Seems I'm ahead of GitHub available versions:

  Version 3.13 was not found in the local cache
  Error: The version '3.13' with architecture 'x64' was not found for Ubuntu 22.04.
  The list of all available versions can be found here: https://raw.githubusercontent.com/actions/python-versions/main/versions-manifest.json

Made Draft for now, and I'll check back later to rerun tests once 3.13 is available.

[cpswan]

@gkc tests are now passing as the underlying dependencies have slid into place, so this is ready to go now.