Have NPVC act as BrightnessMirrorShowingInteractor

That way, it can intercept the flow and make sure that we don't dismiss
the mirror until the alpha 0 -> 1 animation has finished.

Test: manual
Fixes: 379324369
Flag: com.android.systemui.qs_ui_refactor_compose_fragment

Change-Id: I5c2cbb8081386a8ffa8757c6bc4b5127017cc863