Add model support for design events

What does this MR do?

This MR adds support at the model level for design activity, allowing us to add new events that target DesignManagment::Design objects.

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

This includes changes to the event model and specs at the model level.

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

Part of #33051 (closed)