[web/test] Drop folder cube dependency
Copy useful schema bits, define IBreadCrumbs adapter for Folder/fild_under
(previously relying on ITree adapter) and adjust unittest_viewselector tests
to drop a view that does not exist anymore.
Related to #5168939.
[web/view/treeview] add a 'selected' class on <li> if the entity's url is the currently displayed url
An alternative would be to refactor the corresponding view so that controlling
css classes wouldn't require overriding a 5O-lines method.
Notice by default there is no associated class in the CSS so there is no
rendering difference unless one explicitly add rule in his CSS file.