Add support for projects and additional attributes in Group GraphQL query

Building off of https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/27492, add in support for querying :projects in the Group GraphQL query.

Also add in support for :statistics, :custom_attributes, and :shared_projects. For EE, add :ldap_cn, :ldap_access, :ldap_group_links, :checked_file_template_project_id, :shared_runners_minutes_limit, and :extra_shared_runners_minutes_limit

Related to https://gitlab.com/gitlab-org/gitlab-ce/issues/54520

Look at spec/requests/api/groups_spec.rb to help add any specific group/project related specs