sepolicy-legacy-um: poweroffalarm_app: Add power off alarm app

Make power off alarm app as an independent app domain so that
the sepolies will not affect other apps.
[Giovix92]: Adapt it to lineage-18.1

CRs-Fixed: 2113144
Original Change-Id: Ia80575b6dea893bde30636b9a814a6f20ea54b6f

Change-Id: Ie56c5cbade7332a145f10cd5fff0955bcfc724ef