Merge branch 'mg-add-sidekiq-concurrency-option' into 'master'

Add concurrency option on sidekiq-cluster CLI

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/143329



Merged-by: Bob Van Landuyt <bob@gitlab.com>
Approved-by: Bob Van Landuyt <bob@gitlab.com>
Co-authored-by: Gregorius Marco <gmarco@gitlab.com>