R1:fc34554892ec

Replace "bin/people profileimage" with "bin/user enable|empower"

Summary:
Ref T13382.

- Remove "bin/people profileimage" which previously generated profile image caches but now feels obsolete.
- Replace it with "bin/user", with "enable" and "empower" flows. This command is now focused on regaining access to an install after you lock your keys inside.
- Document the various ways to unlock objects and accounts from the CLI.

Test Plan:
- Ran `bin/user enable` and `bin/user empower` with various…