Feat 4612 real time metrics for kube nodes (#4708)

* feat(k8s/node): display realtime node metrics GH#4612

* feat(k8s): show observation timestamp instead of real timestamp GH#4612

Co-authored-by: Simon Meng <simon.meng@portainer.io>

app/kubernetes/metrics/rest.js

@@ -20,6 +20,10 @@ angular.module('portainer.kubernetes').factory('KubernetesMetrics', [
             method: 'GET',
             url: podUrl,
           },
+          getNode: {
+            method: 'GET',
+            url: `${url}/nodes/:id`,
+          },
         }
       );
     };