Fix temperature handler to always run regardless of sample from throttling callback

* Add unit test to verify that the handler will periodically run
* Add and move debug logs behind DEBUG flag

Test: atest ThermalManagerServiceTest#testGetThermalHeadroom_handlerUpdateTemperatures
Flag: EXEMPT bugfix
Bug: 404630413
Change-Id: I31763ff3ac92db6f2d93c7dd7893a6d4ccbfd717