Create system notes for design events

What does this MR do?

Adds a queue needed by https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/14791

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry for user-facing changes, or community contribution. Check the link for other scenarios.
• 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

Performance and Testing

This is a backstage change entirely aimed at satisfying the ee-spefic-files-check. It does not need its own tests.