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/components/datatables/nodes-datatable/nodesDatatable.js

@@ -9,5 +9,6 @@ angular.module('portainer.kubernetes').component('kubernetesNodesDatatable', {
     orderBy: '@',
     refreshCallback: '<',
     isAdmin: '<',
+    useServerMetrics: '<',
   },
 });