Enhancement: Admin settings users section uses graph api for role assignments

We've switched over to utilizing user role assignments data from the graph api instead of the custom settings api.
Especially for the list view this leads to improved performance.

https://github.com/owncloud/web/pull/8261
https://github.com/owncloud/web/pull/8330
https://github.com/owncloud/web/pull/8418
