[MAINT] - Update support for python versions

[peytondmurray]

Context

Currently we support python>=3.8, and functionally speaking python<3.13 because conda hasn't released support for 3.13 yet. However active support for 3.8 ended 3.5 years ago and there is additionally no longer security support.

Let's find upgrade paths for supporting 3.13 and for dropping old versions.

Value and/or benefit

Maintaining compatibility with old versions costs developer time, CI time, and prevents us from using new features, like fancy type annotations.

[soapy1]

Also sharing https://devguide.python.org/versions/. Python 3.8 EOL was on 2024-10-07

[trallard]

We should drop Python 3.8 right away and 3.9, I would say (as this is now only in security mode) https://devguide.python.org/versions/

I would suggest that moving forward, we only support the last four major Python versions (3.10-3.13 in this case, similar to https://scientific-python.org/specs/spec-0000/#implementation).

Let's find upgrade paths for supporting 3.13 and dropping old versions.

We should already be testing this in our CIs for 3.13. If necessary, let's open a separate issue to track the required updates for 3.13 compatibiity.

[trallard]

Closing this issue as completed through #973