Add support for power component states to PowerStats

This is done in preparation for adding MobileRadioPowerStatsCollector.
Mobile radio has multiple different states (3G, LTE, NR etc) and
multiple different signal levels. The space of all states is vast,
but sparse. This CL prepares to handle per-state stats without
wasting too much RAM and disk space.

Bug: 323970018
Test: atest --host FrameworksCoreTestsRavenwood PowerStatsTestsRavenwood

Change-Id: I76841a59a385f5df0fcc957f5b00116b68d34250