Retire testing support for Python 3.9 and add support Python 3.13

[valeriupredoi]

Description

This is to test support for Python 3.13, and eventually, implement it in PyActivestorage 🐍

We are also retiring testing support for Python 3.9, which has ended.

Before you get started

Checklist

• This pull request has a descriptive title and labels
• This pull request has a minimal description (most was discussed in the issue, but a two-liner description is still desirable)
• Any changed dependencies have been added or removed correctly (if need be)
• All tests pass

[valeriupredoi]

fully supporting Python 3.13 🐍