All Sidekiq workers must use their own queue
Currently we have way too many workers using the "default" queue. Not only does this make monitoring harder, it also leads to the queue getting clogged by slow jobs. The easiest and most robust solution is to simply have every worker use its own queue. The "default" queue in turn must not be used, and we should add some sort of Rubocop rule to enforce this. The queue names should be similar to the worker class names, though they can be something different if it makes sense; as long as the name is descriptive enough.