Fix BatteryInfo using enhanced estimate for charge time

Due to a typo in BatteryEstimates the enhanced estimate we use
for discharging would also be used for charging. This CL corrects
the typo and adds a simple test to catch a similar mistake in the
future. We were also always loading the enhanced estimate even when
we were not using it. As a ~*bonus*~ it should also help improve
the speed of the charging use case for this screen and fixes an
issue with the battery not switching to the charging icon in the
main battery page.

Test: robotest
Bug: 62738028
Bug: 62873396
Bug: 62784575
Bug: 62736144
Change-Id: Ib2cbdeea22afb7da590b701b84f526bdac243410