Enable dual-namespace polling for sidekiq probe in gitlab-exporter

What does this MR do?

This MR enables dual-namespace polling for sidekiq probe in gitlab-exporter. This sets up the metric labels for an upcoming sidekiq namespace deprecation in the next release. The user is not expected to disable dual probing since this needs to be in place for upgrade into the next minor version release when the use of the namespace in sidekiq is deprecated.

Related issues

gitlab-com/gl-infra/scalability#2288 (closed)

Test plan

1. Deploy the chart from this branch.
2. kubectl exec into the Toolbox Pod.
3. Run curl http://gitlab-gitlab-exporter:9168/metrics.
4. Confirm that both namespaced="false" and namespaced="true" appear in the logs.

git@gitlab-toolbox-68b888565-95g4j:/$ curl -s http://gitlab-gitlab-exporter:9168/metrics | grep namespace | tail
sidekiq_jobs_retry_size{namespaced="false"} 0
sidekiq_jobs_dead_size{namespaced="true"} 0
sidekiq_jobs_dead_size{namespaced="false"} 0
sidekiq_default_queue_latency_seconds{namespaced="true"} 0
sidekiq_default_queue_latency_seconds{namespaced="false"} 0
sidekiq_processes_size{namespaced="true"} 1
sidekiq_processes_size{namespaced="false"} 0
sidekiq_workers_size{namespaced="true"} 0
sidekiq_workers_size{namespaced="false"} 0
gitlab_database_rows{query_name="namespaces",type="User",visibility_level="20",root="true"} 1.0

Author checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion.

Required

• Merge Request Title and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
• When ready for review, follow the instructions in the "Reviewer Roulette" section of the Danger Bot MR comment, as per the Distribution experimental MR workflow

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated: Omitted as users are not expected to disable these since both keys need to be enabled for smooth upgrade as described in gitlab-com/gl-infra/scalability#2288 (closed).
• Tests added/updated
• Integration tests added to GitLab QA
• Equivalent MR/issue for omnibus-gitlab opened gitlab-org/omnibus-gitlab!7141 (merged)
• Equivalent MR/issue for Gitlab Operator project opened (see Operator documentation on impact of Charts changes)
• Validate potential values for new configuration settings. Formats such as integer 10, duration 10s, URI scheme://user:passwd@host:port may require quotation or other special handling when rendered in a template and written to a configuration file.