Update subtitle for apps in battery settings

1. If it is a normal app, show "Screen usage TIME"
2. If it is a hidden app, show "TIME"

Note that in this case the item screen will show "TIME"

Bug: 62422404
Test: RunSettingsRoboTests
Change-Id: Ie8d6caf998d18994ac158f0217109c0e5e9f92ba