port 36234-nav-add-groups-dropdown to EE
What does this MR do?
Port of https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/18280 to EE.
What are the relevant issue numbers?
Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/36234.
Port of https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/18280 to EE.
Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/36234.