Skip HeadsUpManager for silent updates

Bug: 401068530
Test: sent HUNs marked group summaries
      => no calls to HeadsUpManager for silent grouping updates
Test: send status bar chip, tap chip
      => HUN shows
      tap chip again
      => HUN hides
Flag: com.android.systemui.notification_skip_silent_updates
Change-Id: Ib62ef56c3c1e5dc32d2d75dc1a734c056ad43719