Fix lock icon not showing on hub after exiting the edit mode

Add a ViewModel for Gone->GH transition. As we now show the hub
before the device is locked and the transition starts.

Bug: b/325108777
Test: manually by exiting edit mode and verifying lock icon animates in
Flag: com.android.systemui.communal_hub
Change-Id: Id1b2450445fe538f1ee9a4611e1d6d07f695c2f9