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)).

This MR is branched from !41714 (merged) and has it as an MR dependency.

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