CI(Ubuntu): Install latest version of Python (3.13) for full config
Enables the full config of Ubuntu to not use the OS-provided python version, but a specific version. Here, we start testing for Python 3.13. For the min config, the runner image provided version will be used. ~~If ever we switch to Ubuntu 24.04, we would have Python 3.12.~~ Edit: we have switched to 24.04
This PR will have some failures that will need help to solve. Python 3.13 is going to be out on Oct 1, 2024. I'm not too much interested in solving these, but I prepared the CI to try it out.
Release of Python 3.13 is tomorrow.
It seems there's a way to ask for numpy to use the old string representation:
https://github.com/astropy/astropy/pull/15096 + references
https://github.com/astropy/astropy/pull/16416