Workspace overlays are not loaded for container children in page preview

[hannesbochmann]

No workspace overlays are loaded inside the page module in a workspace for container children. This can be seen if a child of a container gets hidden and no hidden-overlay (icon overlay for hidden records) is loaded. It seems like the child never got hidden but it is. If the container itself gets hidden the hidden-overlay is displayed correct.

[hannesbochmann]

I'm not sure if my fix is perfect. Maybe it's better to load the overlay in GridElementsHelper::getChildren to always have the overlay but I simply based my approach on the ShortcutPreviewRenderer.