Option to customize Sidekiq service on a worker level

[krasnoukhov]

Here is use case we have: some of the jobs are long-running by design (up to 30 minutes) which skews average for the whole service.

We want to keep average latency monitoring as it is for the rest of the jobs, so the way I see it we can just extract slow ones to be reporting to a separate service.

I'm going to create a PR for this