Migrate SysUI theme to UiMode

Legacy RRO was deleted and resources migrated to DeviceDefault theme.
Theming via overlays is still possible, but the overlay should provide
both themes: day and night.

Test: adb shell service call uimode 4 i32 1
Test: adb shell service call uimode 4 i32 2
Change-Id: I5dee2f94764c5c2f4e11cfabfff97656b3822e8a