Add Settings keys for sticky emergency gesture UI

These will be used to temporarily disable some user navigations when emergency UI is triggered. The usage will be similar to that of Settings.Secure.USER_SETUP_COMPLETE. Adding to backup deny list because they represent internal states and are not user configurable.

Bug: 256494850
Test: manual
Change-Id: I81d46267b79302e87609bea599c94ef7bddeb47f