containments/desktop: properly map position to find the mouseover item
GridView.itemAt() is documented to accept coordinated in contentItem coordinates. passing coordinates in view coordinates will cause items to not be found if contentItem position is not 0,0
With right align, the contentItem is aligned to the right edge of the view and items are positioned from there at negative x coordinates.
(cherry picked from commit 509b655e)
509b655e containments/desktop: properly map position to find the mouseover item
Co-authored-by: Marco Martin notmart@gmail.com