DevOps: Add unit testing step to the pr_checks_backend workflow

[zackdreitzler]

Describe the task

Add a unit testing check to any PR impacting the data directory and its sub directories. This check ensures that new python code is passing all unit tests

Acceptance Criteria

• [ ] A unit test checking step exists on the pr_checks_backend workflow
• [ ] When no issues are found, report a success to the PR that triggered this action
• [ ] When one or more issues are found, report a failure to the PR that triggered this action

Additional context

This story is currently blocked until #638 is completed. This story is also blocked pending a decision on what python unit test suite to use.

[nlebovits]

Issue #638 has been addressed so this ticket is ready to be worked on. Plus, we now have a unit test to run.

[github-actions[bot]]

This issue has been marked as stale because it has been open for 30 days with no activity.