Simplifyling widget inflation and addition flow.

> Removing insert parameter used to select the index of the view.
  ShortcutAndWidgetContainer no longet relies on the index and instead
  uses x and y to refer a particulat view.
> Creating helper methods to easily insert the icon by passing ItemInfo
  directly. LauncherModel.addItemToDatabase synchronously updates the
  ItemInfo with proper postion information. So we can directly use the
  info instead of passing each parameter separately.

 Bug: 32904959

Change-Id: I021c1b818f2f42604b95a6970e06aacc7211292a