Update previews on color config change (2/2)

Refresh Launcher preview and clock preview when colors are updated. Also
adjust dark mode so the value isn't sent to Launcher when it's the same
as the current value.

Flag: com.android.systemui.shared.new_customization_picker_ui
Test: manually verified
Bug: 288312530
Change-Id: I50879e29c077997aea6be96bb947a589d68d5f0e