Expand and expose Lockdown global action

This action puts the phone into the state where it can only be unlocked
via the user's primary knowledge factor. In the future this can also
evict keys and otherwise secure the device beyond the norm in a sketchy
situation.

This is currently controlled Settings.Secure.LOCKDOWN_IN_POWER_MENU, it
can be enabled for testing via
`adb shell settings put secure lockdown_in_power_menu 1`

Bug: 37221346
Test: Manual
Change-Id: I6197fadf655e5298cab1ab95153c316b87f3b718