Support slice deep links highlighting menu entries

- Add an interface to get highlight menu key resource in Sliceable
- Force implementing the new interface in TogglePreferenceController and
  CustomSliceable at syntax level
- Update the slice index db schema

Bug: 204695404
Test: manual, robotest build pass, unit
Change-Id: I0b5068bccd04f1590023de7f3385bc0a4c6fa47b