Add a remove action to the service to add pages to favorites, to make it a complete API

For XFAV-3 , a service was added to add a page to the favorites list.

This issue is about embellishing this service with the possibility to remove the page from the favorites as well (not only add), so that it's a "complete" service that can be used as an API by a different UI than the standard one from the panel (and also that a new standard UI can be added for removing a page from the favorites when on the page).

However, the objective is not to add the remove UI as part of this issue.