Use new time format in BatteryInfo

1. Using "h" and "m" instead of "hrs" and "min"
2. Refactor the string to CharSequence so it won't have
TTS issue(i.e read "m" as "meter")
3. Update tests related to this part.

Bug: 37201139
Test: RunSettingsRoboTests
Change-Id: I9cadb511572b2d522d26ab337c171fa69da87475