Support the new `app.kubernetes.io` labels in a backward compatible way

[consideRatio]

The JupyterHub Helm chart and KubeSpawner now provides app.kubernetes.io labels that supersedes the old app and component labels. So instead of app one can use app.kubernetes.io/name and instead of component one can use app.kubernetes.io/component.

I figure we could make the dashboards work even without scraping details for the labels app and component. So for example, we would transition like this for the panels that references label_app:

 # Sum up all running user pods by namespace
 sum(
   # Grab a list of all running pods.
   # The group aggregator always returns "1" for the number of times each
   # unique label appears in the time series. This is desirable for this
   # use case because we're merely identifying running pods by name,
   # not how many times they might be running.
   group(
     kube_pod_status_phase{phase="Running"}
   ) by (pod)
-  * on (pod) group_right() group(
-    kube_pod_labels{label_app="jupyterhub", label_component="singleuser-server"}
-  ) by (namespace, pod)
+  * on (pod) group_right() (
+    group(
+      kube_pod_labels{label_app_kubernetes_io_name="jupyterhub", label_app_kubernetes_io_component="singleuser-server"}
+    ) by (namespace, pod)
+    or
+    group(
+      kube_pod_labels{label_app="jupyterhub", label_component="singleuser-server"}
+    ) by (namespace, pod)
+  )
 ) by (namespace)