Draft: Remove legacy Design Management frontend

What does this MR do and why?

Removes legacy Design Management frontend as it is no longer used.

Issues are work items, and there we use app/assets/javascripts/work_items/components/design_management, and the places where the legacy Issues view is used are following types; Incidents, Tickets, Test Cases, and Requirements. And none of these types support design management. In this MR, following view hierarchy was updated;

• app/views/projects/issues/show.html.haml
  • app/views/projects/issues/_details_content.html.haml - The usage of app/views/projects/issues/design_management removed from here.
    • app/views/projects/issues/_design_management.html.haml - This view mounts app/assets/javascripts/design_management, mountpoint was removed.
      • app/assets/javascripts/design_management - This entire directory and its corresponding Jest specs are removed.
• QA spec referencing legacy design management is also removed.

References

• &17987
• #520791
• #574498

Screenshots or screen recordings

NA

How to set up and validate locally

View Issues (with designs attached) as well as Incidents, Test Cases, and Service Desk tickets to ensure that the pages render correctly.

MR acceptance checklist

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