thermal: IThermal V1.1, add methods to send thermal throttling events

Add IThermalCallback and IThermal::registerThermalCallback() method.
Frameworks code calls this method to register a callback used by the
IThermal HAL implementation to send thermal events to the framework
ThermalService.

Bug: 30982366
Test: VtsHalThermalV1_1Target on marlin
      manual test on marlin using marlin 1.1 HAL with modified
      thermal-engine.conf and temporary debug code for notification
Change-Id: Ib49ad93a9495e3af515fced4e46f20186661fe07