Allow PowerUI / platform_app to use thermalservice for receiving
notifications of thermal events.
Bug: 66698613
Test: PowerNotificationWarningsTest, PowerUITest,
manual: marlin and <redacted> with artificially low temperature
threshold and logcat debugging messages
Change-Id: I5428bd5f99424f83ef72d981afaf769bdcd03629
Merged-In: I5428bd5f99424f83ef72d981afaf769bdcd03629