Render group namespaces in clusters index

app/views/clusters/clusters/_cluster.html.haml

@@ -3,6 +3,12 @@
     .table-section.section-60
       .table-mobile-header{ role: "rowheader" }= s_("ClusterIntegration|Kubernetes cluster")
       .table-mobile-content
+        - if cluster.group_type? && cluster.group.id != clusterable.id
+          - if cluster.group.ancestors.any?
+            = "#{cluster.group.ancestors.first.name} /"
+            - if cluster.group.ancestors.length > 1
+              = "… /".html_safe
+          = "#{cluster.group.name} /"
         = link_to cluster.name, cluster.show_path
         - unless cluster.enabled?
           %span.badge.badge-danger Connection disabled