Allow user to filter epics by reaction emoji

What does this MR do?

Expose filtering epics by reaction emoji to the GraphQL API.

The backend portion only of !57452 (merged) which had to be reverted due to multi version incompatibility.

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

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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
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Security

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• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Related to #325630 (closed)