Move multiple issue boards frontend to core (CE-backport)
This moves multiple issue boards for projects to core / CE. It is the frontend part of https://gitlab.com/gitlab-org/gitlab-ce/issues/53811. Multiple issue boards for groups remain unaffected.
CE-backport of https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/14514
Edited by 🤖 GitLab Bot 🤖