ENG-10202 - Defining eligible additional reviewer relationships

Feature Flag

The Additional Reviewer field in the Profile should accept any employee unless they have one of the following relationships to the User:

1. Direct Manager (existing reviewer)

2. Direct Reporters and drill-down reporters (to avoid reviewer loops)

3. Current user (the user in question)

4. Not-active users

Andrii did the initial work on this feature and all this work should build on https://github.com/15five/fifteen5/pull/29538/files