Add idle screen brightness mapping to DPC

Add idle screen brightness nits mapping to config.xml.
Also add flag to enable idle screen brightness mode.
Add idle screen brightness mapping to DPC dumpsys.

Bug: 205685949
Test: adb shell dumpsys display | grep -A10 Idle
Test: atest BrightnessMappingStrategyTest

Change-Id: Ifa18b835c05c28c060c46c77aeaeca457a2b12e3
5 files changed