power/stats: Add VTS testcases

VTS testcases to test following APIs:
1. getRailInfo(...)
2. getEnergyData(...)
3. streamEnergyData(...)

BUG: 118365266
BUG: 111185513
Test: run vts -m VtsHalPowerStatsV1_0Target
Change-Id: Ie90ecfae937beebf96a9d66eb4b10954242ad07b
2 files changed