Drop support for Python 3.7

[jeffwidman]

Code improvement description

Python 3.7 was EOL'd at the end of June:

• https://devguide.python.org/versions/
• https://peps.python.org/pep-0537/#lifespan

We will be dropping support for Python 3.6 later this month:

• Drop support for Python 3.6 #6299

And as part of that we plan to also drop official support for Python 3.7 as well. This ticket tracks actually doing the technical work / PR's to drop 3.7.

[jeffwidman]

https://github.blog/changelog/2023-08-02-deprecation-notice-dependabot-to-drop-support-for-python-3-6-and-3-7/