Added FolderIconPreviewVerifier class.

This class verifies whether an item in a Foder is displayed in
the FolderIcon preview, based on the item's rank.

We use this class to determine which items in a Folder will be
displayed in the preview.

Bug: 35064148
Change-Id: Ia21bccbd95c348efeac62591ae3696a4c60b5339

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

@@ -98,10 +98,4 @@ public class StackFolderIconLayoutRule implements FolderIcon.PreviewLayoutRule {
     public boolean clipToBackground() {
         return false;
     }
-
-    @Override
-    public List<View> getItemsToDisplay(Folder folder) {
-        List<View> items = folder.getItemsInReadingOrder();
-        return items.subList(0, Math.min(items.size(), MAX_NUM_ITEMS_IN_PREVIEW));
-    }
 }