Add Project.forkedFrom to graphql api

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/183115



Merged-by: Max Woolf <mwoolf@gitlab.com>
Approved-by: Andrew Jung <ajung@gitlab.com>
Approved-by: Max Woolf <mwoolf@gitlab.com>
Approved-by: Ashraf Khamis <akhamis@gitlab.com>
Co-authored-by: Niklas <mc.taucher2003@gmail.com>