Add support for Django 5

[camuthig]

This makes changes and adds testing for Django 5.0, 5.1, and 5.2.

A new cached property called accessor_name was added in 5.2 for performance improvements that this package needs to mimic. This uses the same value as get_accessor_name, which is how it is also implemented in core.

See: https://code.djangoproject.com/ticket/35230