Remove EOL versions

[calumy]

This PR removes the following end-of-life versions of Python and Django:

• Python 3.6 - EOL: 23rd December 2021
• Python 3.7 - EOL: 27th June 2023
• Django 3.2 - EOL: April 2024

In addition to removing the EOL versions, the Django upgrade pre-commit hook has also been added, and fixes are included in this PR. These changes relate to:

• The use of USE_L10N, which was deprecated in Django 4.0: https://github.com/adamchainz/django-upgrade?tab=readme-ov-file#use_l10n
• The use of re_path, which has been rewritten using the path() syntax added in Django 2.0: https://github.com/adamchainz/django-upgrade?tab=readme-ov-file#urls

[johnraz]

I was thinking we could merge this after the next release, like that we can issue a warning that this will be the last release to support all those older versions.

[calumy]

Drafting until #342 is merged and a new version released.

[giovannicimolin]

@calumy This is awesome, thanks for the contribution here!

I think we can get this in shortly after our first Jazzband release.