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
Test: atest DisplayPowerControllerTest
Test: atest DisplayPowerController2Test
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:5b267f70a6fcad1b161ee9cf54c2a832f567cf33)
Change-Id: I2369d10c293d7b05d55878a28f702a81428ddd15