Add FallbackTaskbarUIController

- Refactor TaskbarManager to accept StatefulActivity instead of BaseQuickstepLauncher
- Update the new StatefulActivity in onOverviewTargetChange()
- Cleanup LauncherTaskbarUIController a bit to avoid initializing TaskbarActivityContext, TaskbarDragLayer, and TaskbarViewController in the constructor, and instead get these from mControllers after init()

Test: No change in behavior
Bug: 188790554
Change-Id: Ic4d69d73deb6dada416876eb265db57803c3adfd

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

@@ -253,6 +253,14 @@ public class TaskbarViewController {
         mTaskbarNavButtonTranslationY.updateValue(-deviceProfile.getTaskbarOffsetY());
     }
 
+    /**
+     * Returns whether the given MotionEvent, *in screen coorindates*, is within any Taskbar item's
+     * touch bounds.
+     */
+    public boolean isEventOverAnyItem(MotionEvent ev) {
+        return mTaskbarView.isEventOverAnyItem(ev);
+    }
+
     /**
      * Callbacks for {@link TaskbarView} to interact with its controller.
      */