power/stats: Add VTS tests for power stats hal am: c357e98dcc am: 3130674ac3

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/1576533

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I0d9882b9d4ecaa709b3357251d9bae7b064ffe9a