Installs ingress (using helmfile)

Also supports custom values.yaml file as well

Part of gitlab-org/gitlab#7983 (closed)

Testing

See also pipeline for this MR

Without custom .gitlab/managed-apps/ingress/values.yaml file

https://gitlab.com/gitlab-org/cluster-integration/cluster-applications/-/jobs/338571650

With custom .gitlab/managed-apps/ingress/values.yaml file

https://gitlab.com/gitlab-org/cluster-integration/cluster-applications/-/jobs/339046804