Run sidekiq-server middleware in all specs

What does this MR do?

Run sidekiq-server middleware for all specs using sidekiq-inline. Since the middleware chain is now used for all specs, we should make sure modifications do not bleed into other specs. So this adds a cop and helper method to help with that.

For gitlab-com/gl-infra/scalability#296 (closed)

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• [-] Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done