Data providers that provided data for multiple entities were being added
to the data structure as nullptr due to move semantics. Now they will
only be added once (ensuring no more nullptr entries) and an index will
map each power entity id to its corresponding data provider.
Bug: 184290936
Test: Presubmit
Change-Id: I858269beb36ba5f87bb14a228079f3abd6c2332f
Also cleaning up Power Stats HAL type names to be less verbose
Bug: 176117316
Test: atest VtsHalPowerStatsTargetTest
Change-Id: I252a13b0490326ab9557f4a81ee313e57eb36754
Merged-In: I252a13b0490326ab9557f4a81ee313e57eb36754