ApplicationPage: Do not use Item.visible to calculate the visibility of the parent
Having the parent visible=false will make all children visible:false so it becomes a silly exercise.
Instead, use a property made for this that doesn't have other connotations.
It kind of feels like we are workarounding a bug in the layout class but this is needs addressing now.
(cherry picked from commit 101c0149)
Co-authored-by: Aleix Pol aleixpol@kde.org