Allow operator/manufacturer setting to use priority

This allows apps which use OPERATOR_SETTING or
MANUFACTURER_SETTING intent to use priority.
The apps can put their setting in any position
in the dashboard of Settings app.

Bug: 29143388
Test: manual - installed SettingsTests.apk using priority into priv-app
               and opened Settings app

Change-Id: Ie5df36e8f3ed704583b1559c16ee3719c7545271