Drop Python 3.9 support when it goes EOL

[ni-jfitzger]

Description of issue

When Python 3.9 goes EOL In October 2025, we should drop support for it.
As part of this, we should also drop our usage of the pkg_resources module, which is part of setuptools, and not a built-in module.

When we added support for Python 3.12, we shifted toward using the built-in importlib.metdata module, instead.