Measured screen energy into BatteryStatsHelper

Use measured screen energy usage (where available)
in battery reporting in BatteryStatsHelper, including
total and per-app screen energy usage.

Regardless of the data source (measured screen power usage vs.
estimating from screen time), the blame on apps is 'smeared',
meaning that it is apportioned (after-the-fact) based on each
app's foreground usage. That does not change here.

Also fixes a mistake in Uid.getScreenOnEnergy().

Future followups to do
1. Make getMeasuredOrEstimatedPower more universal (as more
   PowerCalculators follow suit)
2. Support for BatteryUsageStats
3. Deal with voltage properly
4. Toggle whether to report the measured energy on/off.

Test: atest BatteryStatsHelperTest
Bug: 174818228
Change-Id: I0eaa4bc594cb31b4a26b5488b08114cbf80e3884