RFC: Set timeout for Sidekiq when shutting down

What does this MR do?

Set the timeout for sidekiq which it honours during shutdown.

The main issue is actually one in the GDK, where sidekiq doesn't respond to a gdk stop rails-background-jobs within 7 seconds. This was making Runit time out and failing to stop or restart the service.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content