Various icon cache fixes

> Multiple instances of LauncherIcon created when
    LauncherIcons refers IconCache which in turn creates new LauncherIcons
> Widget icons are never cached as they were using low res icons
> Shortcut drag icons are not loaded synchronously
    when using PinItemRequest flow
> Wrong lastUpdatedTime is used in iconCache for shortcuts
> IconUpdateHandler does not ignore managedUser promise icons

Change-Id: Ie7eed68a30fad11d1861b6c70c380953a15ae1cf