chore: use only aggregation labels from mimir in unified registry

chore: use only aggregation labels from mimir in unified registry

This makes it so we only use aggregation labels from aggregation sets defined for Mimir for the unified recording rule registry.

Making sure that we're only aggregating what we need.

In practice, this means that we're removing the queue, worker and urgency labels coming from the sidekiqWorkerQueueSLIs aggregation set.

I noticed this when working on gitlab-com/gl-infra/platform/runway/team#185 (closed), for which it woulld be handy to be able to decouple Mimir rules and Thanos rules.