[Settings] Add a verification flow for exiting repair mode

Handles the ACTION_CONFIRM_REPAIR_MODE_DEVICE_CREDENTIAL
intent to launch the confirm device credential activity for
users to exiting repair mode. The activity passes a special
user id USER_REPAIR_MODE to the framework and verify credentials
that the user enrolled in normal mode.

Bug: 277561275
Test: am start -a android.app.action.PREPARE_REPAIR_MODE_DEVICE_CREDENTIAL
      settings put global repair_mode_active 1
      am start -a android.app.action.CONFIRM_REPAIR_MODE_DEVICE_CREDENTIAL
      The credential is verified successfully.
Change-Id: I9ffe32f9925ee2b990c49d5674d27196a4c9edf7