Allow separate configuration of display color fade

Previously color fade before display power-off was disabled for devices
with a low-RAM configuration.  Some devices may not want this animation
even though they have a plenty of RAM, so allow it to be controlled
separately.

Bug: 284838712
Change-Id: I2369d10c293d7b05d55878a28f702a81428ddd15
Merged-In: I2369d10c293d7b05d55878a28f702a81428ddd15
Test: atest DisplayPowerControllerTest
Test: atest DisplayPowerController2Test