This backport adds a test of AwardEmojiPolicy for Epics.

Description from the original CE commit:

Adding new `AddAwardEmoji`, `RemoveAwardEmoji` and `ToggleAwardEmoji`
GraphQL mutations.

Adding new `#authorized_find_with_pre_checks!` and (unused, but for
completeness `#authorized_find_with_post_checks!`) authorization
methods. These allow us to perform an authorized find, and run our own
additional checks before or after the authorization runs.

https://gitlab.com/gitlab-org/gitlab-ce/issues/62826