Summary:
add support for more roles in the model to allow generic delegates

provides roles that will be useable by the generic delegates

allow to retrieve the album or the artist with a generic role from models

support everything except open with generic view and delegate

allow all artsist and all albums models to know each other

this is needed to allow the models to generate proxy models linked to an
artist from an album item for example

makes it possible to open and use album or all albums from an artist views

still some things are not working well like the possibility to show the
artist of an album

I still need to report in the new components all the improvements that have gone since I started this branch

Test Plan: works fine

Reviewers: #elisa, astippich

Reviewed By: #elisa, astippich

Tags: #elisa

Maniphest Tasks: T7671

Differential Revision: https://phabricator.kde.org/D9777