DisplayBrightnessController fixing race with updatePowerState in the middle of setBrightness

setBrightness method delivers brightness to DPC via 2 threads: BrightnessSettings -> mainLopper + DPC -> displayThread
updatePowerState could happen before new brightness is delivered, in this case DisplayManager is not notified about brightness change.

Bug: b/416046693 , b/414262134
Test: atest DisplayPerfTest, atest DisplayBrightnessControllerTest, https://b.corp.google.com/issues/403303379#comment6
Flag: EXEMPT bugfix
Change-Id: I946e219f52a2439ad3405f3b5d7fe5e639d993ac