[FE] Reduce the data being loaded per Design on first load

What does this MR do?

Refactors Design management application to reduce the number of design fields fetched on the initial load of the main design view.

This MR changes the way we fetch a single design: previously, we fetched all designs with all required fields when opening a design view. Now, we fetch just a few fields for designs list and all the discussions and notes for single design view.

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

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

Related issues

#34408 (closed)