The usage of KActionCollection makes KBookmarks depend on KXMLGui. To allow to get rid of this rather heavy dependency for KF6 a new constructor is introduced that does not take a KActionCollection. Instead apps that use KBookmarksMenu and KXMLGui are encouraged to manually add the relevant actions to their action collection. It's not pretty, but better than depending on KXMLGui, especially given that KIO depends on KBookmarks and thus on KXMLGui.