Adds an observer to HighBrightnessModeController to monitor the system's
thermal status and ensure HBM is off if the status is above the new
limit defined in the display-device-config file.
Also fixes a bug where AutomaticBrightnessController does not
automatically recalculate a value when HBM mode changes and the ambient
lux does not.
Bug: 179019497
Test: atest HighBrightnessModeControllerTest
Change-Id: I38a805671cee0f63e858b7ec0b6a45ca43df1737
8f1a5c14ad