[VETS-API] Backend CI - Expanded BE Team approach

[ryan-mcneil]

The work here lead to the realization that we need to simplify our approach. Chatting with a couple BE folks, and getting approval from Clint, we've decided we're going to modify our approach by including members from the "exempt team" (Mobile, LH, Identity) in the backend-review-group and they will be tasked with approving their greater teams' respective PRs. This will require reworking (and simplifying) the work done in this PR, and testing.

Tasks

• Rework the work done in the ticket/PR linked above to remove checks for "exempt" teams, but add in step to request approval from specific individuals on those exempt teams (who will also be added to the backend team)
• Test locally and in "production"

Acceptance Criteria

• Workflow is merged to master and everyone is happy.