appDisplay: Use a custom LayoutManager for the AllView stack

ClutterBinLayout uses the maximum width/height of all children in
size requests and positions children according to the expand/align
properties. This means that the vertical position of folder popups
is not considered in size requests, so if the main view is smaller
than a folder popup's height and offset, the popup will be truncated
and/or mispositioned. Fix those cases by using a custom LayoutManager
that behaves like ClutterFixedLayout for height requests and like
ClutterBinLayout otherwise.

https://bugzilla.gnome.org/show_bug.cgi?id=694371