Controls UI - Handle activity dismissal from dialog

When the task stack indicates a removal, from say the back gesture,
also close the dialog.

Bug: 157664596
Test: Use back gesture within panels
Change-Id: I60beb61a58677b686d1fad5cf72bb38786cd5f34

packages/SystemUI/src/com/android/systemui/controls/ui/DetailDialog.kt

@@ -64,6 +64,10 @@ class DetailDialog(
         }
 
         override fun onActivityViewDestroyed(view: ActivityView) {}
+
+        override fun onTaskRemovalStarted(taskId: Int) {
+            dismiss()
+        }
     }
 
     init {