Polish all apps taskbar unstash behavior for transient and persistent.

- During gestures from taskbar all apps, unstash immediately in
  transient.
- Overlay closes sooner if all apps is open (still done later for EDU).
- Taskbar stashes in overview when All Apps is opened.
- Transient app-window threshold is ignored if All Apps is opened.

Test: Manual
Fix: 262076812
Change-Id: I46b2dcdc75ee0cc15c1b47da2139ff8c20cf618a

quickstep/src/com/android/launcher3/taskbar/TaskbarActivityContext.java

@@ -887,6 +887,11 @@ public class TaskbarActivityContext extends BaseTaskbarContext {
         return mControllers.taskbarStashController.isStashed();
     }
 
+    /** Returns {@code true} if taskbar All Apps is open. */
+    public boolean isTaskbarAllAppsOpen() {
+        return mControllers.taskbarAllAppsController.isOpen();
+    }
+
     /**
      * Called to start the taskbar translation spring to its settled translation (0).
      */