Add backgroundPermission attr to public-staging.xml

Open "android:backgroundPermission" attr to Apk-In-Apex packages.

Test: atest BackgroundPermissionsTest
Flag: android.permission.flags.replace_body_sensor_permission_enabled
Change-Id: I6a4a3aad59d46b54713dfe10523a389a498b473d
Bug: 364638912
Bug: 364640981
Bug: 360781841