Update BatteryStatsImpl to handle multidisplay

Add screen on and doze timers for multiple displays.

For Battery history, charge/discharge logs and UnsupportedAppUsage, the
legacy screen state timers remain, as well. The legacy timers and
screen state tracking will now track overall screen state of the device.
The current overall screen state is the most "important" state currently
active.
Order of screen state importance is: on, doze, doze suspend, off.

Note: Utilizing per display measured energy will be handled in a follow
up CL.

Bug: 194107383
Test: atest FrameworksCoreTests:BatteryStatsTests
Change-Id: I4ad4f54b6897f406e4ec0f59834dd4762083e0d8