Folder support in Taskbar

- Add TaskbarActivityContext which allows shared Launcher elements to
  "just work" using existing generic ActivityContext.
- TaskbarContainerView extends BaseDragLayer<TaskbarActivityContext>.
- Inflate FolderIcon and Folder using TaskbarActivityContext to be
  shown in TaskbarContainerView.
- Use TaskbarActivityContext's DeviceProfile to determine icon size
  instead of overriding in styles. This also ensures that normal
  BubbleTextView icons have the same size as FolderIcons.

Test: Place a folder in home screen hotseat, ensure it shows up in
taskbar and can be opened, and that apps inside it can be launched
or dragged.
Bug: 171917176

Change-Id: Ic25d2f84bcd7e3399c88989305ea565497c030d9

src/com/android/launcher3/folder/Folder.java

@@ -1616,6 +1616,11 @@ public class Folder extends AbstractFloatingView implements ClipPathView, DragSo
         return false;
     }
 
+    @Override
+    public boolean canInterceptEventsInSystemGestureRegion() {
+        return true;
+    }
+
     /**
      * Alternative to using {@link #getClipToOutline()} as it only works with derivatives of
      * rounded rect.