Add Unicorn and Puma health checks
What does this MR do?
This adds a separate Unicorn and Puma health checks
that are executed on dedicated web_exporter: endpoint.
This gives information whether there are workers available to accept connections to the service.
References
Based on: !17953 (merged) and omnibus-gitlab!3650 (merged)
Part of: #30201 (closed) !17962 (merged)
Related to: #30037 (closed)
Screenshots
Does this MR meet the acceptance criteria?
Conformity
Edited by Grzegorz Bizon