Add AOD metrics in batterystats

Fixes: 64899521
Test: manual - flash build, reset batteryStats, use device > 1 hr
with alternating pattern between screen on/off/AOD. Dump stats, check
all screen related stats look normal, esp. record matches actual time
spent in each screen state. In raw bugreport:
Search "amount discharged" for % discharge;
Search "Screen on/off/doze discharge" for mAh discharge;
Search "time on battery" for up/real time in each state.

Test: Added two unit tests for note AOD screen state
Change-Id: I7193a36751124dd380818b2b665303c0f0d8c984