Enable auto-lock for private space

This change adds the implementation for auto-locking private space. It
adds support for both - auto-lock on device lock and auto-lock on
inactivity. It also adds a bunch of unit tests inside
UserManagerServiceTest for the auto-lock scenarios.

Test: atest UserManagerServiceTest. Also, tested by flashing changes
locally on the device
Bug: 303201022

Change-Id: Iec662ca5e9417843b482496935852974cf445a53