Merge branch 'mk/customize-sidekiq-log-level' into 'master'

Use GITLAB_LOG_LEVEL for Sidekiq server logs

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/149790



Merged-by: Marius Bobin <mbobin@gitlab.com>
Approved-by: Marius Bobin <mbobin@gitlab.com>
Co-authored-by: Mike Kozono <mkozono@gitlab.com>