Initial doze brightness for offload

Use the last observed lux and the doze curve to set the initial doze brightness before the offload session takes over.

Rely on the policy rather than the state - in the first doze power request, the policy is doze but the state is still ON.

Switch to doze auto-brightness mode immediately rather than posting on the handler - we need this so that we get the correct brightness value.

Bug: 325627091
Test: atest AutomaticBrightnessControllerTest
Test: atest BrightnessEventTest
Test: atest BrightnessReasonTest
Test: atest AutomaticBrightnessStrategyTest
Test: atest DisplayPowerControllerTest
Change-Id: I9aaaa1d8b5bb09d5ce5dbe53453bcd28aae2dd8f