Implement android.hardware.health@2.0.

healthd_common.cpp uses health@2.0 for health@2.0-service
and healthd.

charger and recovery will be fixed in a follow up change.
(They still use libbatterymonitor for now).

Test: adb logcat -e "health@2.0"
Test: adb shell lshal --debug

Change-Id: I9ff0691d467df37118d7f143693c1bcd17a5bcbf