Allow selecting all queues with sidekiq-cluster

What does this MR do?

Because it was designed for selecting specific queues, sidekiq-cluster didn't have a convenient method to select all queues. As we want this to become the default sidekiq entry point for all GitLab installations, and the default is to handle all queues in a single process, we need that option.

(This was possible before: using --experimental-queue-selector, you could ask for something like has_external_dependencies=true,false, but that's not obvious.)

Instead of making * a wildcard anywhere, which would be more general, this commit just allows a single * in a queue group to represent all queues. While this is less general, it's also simpler to implement, and we can assume that YAGNI for the wildcards.

For gitlab-com/gl-infra/scalability#169 (closed).

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.