Backend - Zoekt GraphQL implement include forks filter

Background

The legacy Zoekt search API supports include_forked param, but the new GraphQL API does not support the param

Proposal

Support sending include_forked param for the Zoekt GraphQL API

Zoekt filters are passed down in the zoekt_filters method for global in Search::ZoektSearchable, group in EE:Search::GroupService, and project service in EE::Search::ProjectService.

Note: that the param is set to true for project searches, as those should always include forked