Adding MSDL feedback to dragging apps and widgest over drop targets.

The ButtonDropTarget class delivers MSDL feedback onDragEnter.

Test: DeleteDropTargetTest
Test: manual. Verified haptics when dragging apps and widgtes over
  "Remove" and secondary drop areas.
Flag: com.android.launcher3.msdl_feedback
Bug: 371249457
Bug: 371315650
Change-Id: Ic3f79ab5e3da7bb26797f2a1bfb79b5e37b3ac97

src/com/android/launcher3/util/MSDLPlayerWrapper.java

@@ -28,6 +28,9 @@ import com.android.launcher3.dagger.LauncherBaseAppComponent;
 import com.google.android.msdl.data.model.MSDLToken;
 import com.google.android.msdl.domain.InteractionProperties;
 import com.google.android.msdl.domain.MSDLPlayer;
+import com.google.android.msdl.logging.MSDLEvent;
+
+import java.util.List;
 
 import javax.inject.Inject;
 
@@ -58,4 +61,8 @@ public class MSDLPlayerWrapper {
     public void playToken(MSDLToken token) {
         mMSDLPlayer.playToken(token, null);
     }
+
+    public List<MSDLEvent> getHistory() {
+        return mMSDLPlayer.getHistory();
+    }
 }