[Housekeeping]: Drop obsolete Ansible and Python versions and fix tests

[jeffgdotorg]

Proposed Changes

• Drop test coverage for Ansible versions older than v2.15.0, which are now unsupported
• Drop test coverage for Python versions older than v3.8, which are now unsupported
• Update test coverage to get ansible-test sanity passing cleanly with the updated Ansible and Python versions

Justification

This collection has fallen behind the times in terms of the versions of Ansible and Python included in its test suite coverage. Dropping coverage of obsolete versions lightens the maintenance burden and better aligns this collection with current Ansible best practices.

[jeffgdotorg]

Assigning to @minitriga for any needed cleanup. If my PR is worth anything, please use it to whatever extent is helpful, but I have no ego where this is concerned.