Allow filtering of issues by reaction emoji in GraphQL

Summary

It's possible to filter group/project issues by various attributes; such as epicId, milestoneTitle and assigneeUsername (among others). In order to fully support issue lists in Vue we need to support filtering by reaction emoji in the GraphQL API, including by None and Any.

Acceptance criteria

• User can filter by My-Reaction
• User can do None and Any filtering with My-Reaction
• User can do negated filtering with My-Reaction