Use separate queues for all Sidekiq workers

## What does this MR do?

This MR updates all workers so that they (mostly) use their own Sidekiq queues. This in turn allows us to monitor queues more accurately and in the future impose queue specific throttles, limits, etc.

This is a critical part we need in 8.13, despite it being so close to release day.

See https://gitlab.com/gitlab-org/gitlab-ce/issues/23370 for more information.

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG.md) entry added
- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/23370

See merge request !7006