Add award emoji to epics in GraphQL

What does this MR do?

This MR adds award emoji connection to epics in GraphQL API in order to be used in Bulk Import functionality that ~"group::import" is building (https://docs.gitlab.com/ee/development/bulk_import.html). We currently import group epics (via GraphQL API) but would like to carry award emoji as well.

Screenshots (strongly suggested)

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