Refine battery text in battery header

1. When there exists estimate time, show it, otherwise
show battery status label.
2. Change the summary based on whether it is charging.
(Estimated time left vs Time to full charge)

Bug: 35328749
Test: RunSettingsRoboTests
Change-Id: I64ee8acd248062b4effcfc58ed908be7d89621a3
4 files changed