Add summary for categories in battery advanced page

If the category only contains one app, show usage time, otherwise
show app with maximum usage.

Also add usage time for apps in battery settings page.

Bug: 35396770
Test: RunSettingsRoboTests
Change-Id: I43fe9c2289535be2c1b95ffded6b52b0ff099589
(cherry picked from commit 3bbaca9c)