Match items in icon preview with items in Folder using permutations.

Before, with the FolderIconPreviewVerifier, we would
adjust which items are displayed in the FolderIcon.
This caused some issues where the apps in the folder
icon would jump to whatever was in the upper left quadrant.

Now, we always display the 4 first items in the icon by
modifying the XY positions of the items within the Folder.

Bug: 27944225
Bug: 35064148
Change-Id: I46c0fbb064d4da4da155e29963bfb92b14e40f07