Adds ability to use LauncherPreviewRenderer in Sandbox.

This is mostly a proof-of-concept for future use and
tweaks as desired by UX.

The idea is to better replicate the actual UI.

Screenshot: https://drive.google.com/file/d/1EGDgcrSH2QZuSh6P3zWLBl6L8Xd-gtFY/view?usp=sharing

Bug: 148542211
Change-Id: Ibed4b8118346ef72599463c9fd6a2f71166993fd

src/com/android/launcher3/WorkspaceLayoutManager.java

@@ -130,12 +130,16 @@ public interface WorkspaceLayoutManager {
         }
 
         child.setHapticFeedbackEnabled(false);
-        child.setOnLongClickListener(ItemLongClickListener.INSTANCE_WORKSPACE);
+        child.setOnLongClickListener(getWorkspaceChildOnLongClickListener());
         if (child instanceof DropTarget) {
             onAddDropTarget((DropTarget) child);
         }
     }
 
+    default View.OnLongClickListener getWorkspaceChildOnLongClickListener() {
+        return ItemLongClickListener.INSTANCE_WORKSPACE;
+    }
+
     Hotseat getHotseat();
 
     CellLayout getScreenWithId(int screenId);