Added API endpoint for Sidekiq Metrics.

What does this MR do?

It adds an API endpoint to gather metrics about Sidekiq, it's jobs, queues, and processes.

Why was this MR needed?

There was no API endpoint for Sidekiq information.

What are the relevant issue numbers?

Fixes #7171 (closed)

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing