Added display white-balance to framework.

Test: manual.
      First, enable DWB with:
        $ adb shell settings put secure display_white_balance_enabled 1
      Then, enable DWB logging with:
        $ adb shell cmd display dwb-logging-enable
      This should start logging the collected, filtered and applied CCT. You can filter it with:
        $ adb logcat | grep -E 'Ambient|DisplayWhiteBalance'

Change-Id: I04747c123739b7b45dfd0c038cc6e20edf113eb0