mgr/dashboard: check if user has config-opt permissions before retrieving settings.

mgr/dashboard: check if user has config-opt permissions before retrieving settings.

Fixes: https://tracker.ceph.com/issues/43595
Signed-off-by: Alfonso Martínez <almartin@redhat.com>
(cherry picked from commit ea1c8c7ef7f494208aec1c59d12fec2da759784a)

 Conflicts:
	src/pybind/mgr/dashboard/frontend/src/app/core/navigation/navigation/navigation.component.ts
	src/pybind/mgr/dashboard/frontend/src/app/shared/components/notifications-sidebar/notifications-sidebar.component.spec.ts
	src/pybind/mgr/dashboard/frontend/src/app/shared/components/notifications-sidebar/notifications-sidebar.component.ts