FE: Allow users to filter epic list by specific group

Summary

This is the frontend issue for the requirements found in Allow filtering by group in epic list and roadmaps (&9431 - closed).

In this issue, we need to Add Group as filter option.

Additional Information

From this comment:

it is possible to ignore descendent groups while fetching an epic for any group and GraphQL query already supports it, so add group::ABC Company to filter to only display results for that group is doable without any additional backend effort, but adding Group token support in filtered search would need updating the query first.