Invert custom views in dark mode

Invert custom view colors (in Y'UV space) if its background isn't dark,
we're in dark mode, and app doesn't target Q.

Change-Id: I74f557315c5e7e91ee7ec01d1535dac40f921524
Fixes: 112767229
Test: send custom notification from pre Q app with black background
Test: send custom notification from pre Q app with white background
Test: send custom notification from pre Q app with green background
Test: send custom notification from Q app with white background