Announce for accessiblity when taskbar is invoked/closed

Test: Manual
Bug: 265620540
Change-Id: I6660be7716ec59c765f3d54f8fe9889eaaf56e10

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

@@ -600,6 +600,7 @@ public class TaskbarStashController implements TaskbarControllers.LoggableTaskba
                 if (!mIsStashed) {
                     tryStartTaskbarTimeout();
                 }
+                mControllers.taskbarViewController.announceForAccessibility();
             }
         });
     }