add dev/perforce-testing-helpers to aid with manual Perforce permissions testing

Created by: ggilmore

This PR adds:

• an example depot that's suitable for manual Perforce permissions testing
• a script that handles uploading the depot at the start of a new round of testing
  • See a video of this script running:
    • 
• a script that creates a test user, associated groups, prompts the user to select the groups they'd the test user to be a part of, and applies a protections table between each test case
  • See a video of this script running:
    • 

See the README for more information.

Test plan

These scripts are external helper tools which aren't used by any of our services. However, I have verified that they work via some manual testing and liberal use of set -x.