feat(force invert): force force-dark if force invert is enabled

Force invert always forces apps dark, even if the developer has used one
of the opt-out APIs. It also ignores the dark theme setting, since that
can be overridden by the app.

Bug: 282821643
Test: atest ViewRootImplTest
Test: manual:
1. `setprop debug.hwui.force_dark 1 && cmd uimode night yes"`
2. Most apps will be dark, except ones that opt-out (e.g. Twitter).
3. `setprop debug.hwui.force_dark 0 && settings put secure accessibility_force_invert_enabled 1`
4. All apps will be dark, regardless if they opt-out (e.g. Twitter).

Change-Id: I61bc6cc5d526324d2d63314bc2ee75160b5326d7