EE backport for gitlab-org/gitlab-ce!29782 (Add service classes for mutating AwardEmoji)

What does this MR do?

This is EE backport for gitlab-org/gitlab-ce!29782 and includes some changes to specs that use methods removed in that MR.

The commit containing the EE changes is https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/15138/diffs?commit_id=7cac6429d0314d43aa22f8c6b708b8fa3e035a49.

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

Performance 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