R1:c86dca3ffc80

Update "bin/policy unlock" to be more surgical, flexible, modular, and modern

Summary:
See PHI1115. Ref T13249. Currently, you can `bin/policy unlock` objects which have become inaccessible through some sort of policy mistake.

This script uses a very blunt mechanism to perform unlocks: just manually calling `setXPolicy()` and then trying to `save()` the object. Improve things a bit:

- More surgical: allow selection of which policies you want to adjust with "--view", "--edit", and "--owner"…