Fix issues with drag and drop from All Apps in non-default grids

=> Also fix the widget tray in these non-default grids, and the external shortcut addition flow. The layout was broken as it was scaling with the icon size. Instead keep it fixed which looks much better, similar to how we maintain all apps.
=> This also fixes a small jump when dragging shortcuts external to Launcher.

issue 154169001

Change-Id: Iad1e3859dd6fedccce9b5c6633e64426a4630c31