mgr/dashboard: Implement profiles for RBD QoS management
Thinking longer-term, an end-user might not like to have to keep copying QoS settings from image-to-image. Instead, it might be better to pre-define QoS levels (e.g. gold, silver, bronze) and the pool QoS defaults and image QoS override would just allow to pick from one of the pre-defined overrides. The profiles could be serialized into the mon's config store and we could add a new librbd configuration option for "rbd_qos_profile_name" that could be applied to the pool/image and would load the values from the mon config store if set.