Override edit mode activity launch animation

This change overrides the glanceable hub edit mode activity launch
animation so that it fades in. It also changes the white background to
transparent so that it doesn't appear as a white flash.

Test: manual
Fix: 425950266
Flag: com.android.systemui.hub_edit_mode_transition
Change-Id: I0ff005bd8b7ae8601e586ae269a7589196584f92