Draft: Add counter metrics in ConcurrencyLimit::ResumeWorker

Sylvester Chinrequested to merge
sc1-concurrency-limit-metric into master

What does this MR do and why?

Add counter metrics in ConcurrencyLimit::ResumeWorker

Using counter metrics allow for more accurate aggregation of concurrency limit data. Gauge metrics may lead to stale values if the GitLab setup has multiple Sidekiq processes writing to separate prometheus metric files.

Changelog: other

Issue: gitlab-com/gl-infra/scalability#3823 (comment 2149241169)

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