Add TaskbarView as a child of Hotseat

Instead of keeping the Taskbar window showing above the home screen,
we now integrate a copy of TaskbarView directly into Launcher's view
hierarchy. Most TaskbarController calls apply to both TaskbarViews
(mTaskbarViewInApp and mTaskbarViewOnHome), except for calls related
to Hotseat, which only apply to mTasbkarViewInApp given the real
Hotseat will be showing with mTaskbarViewOnHome.

More cleanup will follow this change.

Test: All taskbar interactions (e.g. drag and drop) continue to work
Bug: 182512211
Bug: 171917176
Change-Id: I0f0b124f652daa85f866e1df8f9e2981540331a0

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

@@ -84,7 +84,7 @@ public class TaskbarContainerView extends BaseDragLayer<TaskbarActivityContext>
     private ViewTreeObserverWrapper.OnComputeInsetsListener createTaskbarInsetsComputer() {
         return insetsInfo -> {
             if (getAlpha() < AlphaUpdateListener.ALPHA_CUTOFF_THRESHOLD
-                    || mTaskbarView.isDraggingItem()) {
+                    || mTaskbarView.getVisibility() != VISIBLE || mTaskbarView.isDraggingItem()) {
                 // We're invisible or dragging out of taskbar, let touches pass through us.
                 insetsInfo.touchableRegion.setEmpty();
                 insetsInfo.setTouchableInsets(TOUCHABLE_INSETS_REGION);