Create setBrightnessFromOffload method

The method will be used by the offload chip to set brightness temporarily before we get a lux reading. It should not affect the short-term model.
- create a new strategy for the brightness from offload
- add isActive property to the session and don't use offload brightness if the session isn't active

Bug: 307894098
Test: atest com.android.server.display
Change-Id: Ifeef8b26a60f0a04db1937f2b03f1a43335be85e