Add the ability to enable and disable supervision

- Removed the is-enabled command as it was not multi-user aware
- Added enable and disable commands
- Updated dump() to iterate over all known users and dump their supervision state
- Added a UserLifecycleListener to clear data for removed users
- Added unit tests

Test: atest SupervisionServiceTest
Bug: 361098041
Flag: android.app.supervision.flags.supervision_api
Change-Id: Iebe39246be1380b3c8eb23c8668f656f11446ad3