Retain the short-term model when device state changes

- Copy adjustment, userLux and userBrightness to new BrightnessMappingStrategy
- Don't reset the short-term model when a display changes

Bug: 238572374
Test: atest AutomaticBrightnessControllerTest
Test: atest BrightnessMappingStrategyTest
Test: atest DisplayManagerServiceTest
Change-Id: I8a8a3f265c9510bda21abdf0563c02db3e11951e
Merged-In: I8a8a3f265c9510bda21abdf0563c02db3e11951e