Expose copyState on GraphQL DesignCollection type

What does this MR do?

This MR adds a copyState field to the GraphQL DesignCollection type to expose the copy state of the design collection (!42291 (merged)).

A frontend MR !42548 (merged) uses these GraphQL changes.

• Issue: #13426 (closed)

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

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done