app: move appdomain to public policy

Vendor-specific app domains depend on the rules in app.te so they
must reside in public policy.

Bug: 70517907
Test: build
Change-Id: If45557a5732a06f78c752779a8182e053beb25a2
Merged-In: If45557a5732a06f78c752779a8182e053beb25a2
(cherry picked from commit 1f4cab8b)