metropolis/core/metrics: expose containerd metrics endpoint

This adds containerd as another metrics endpoint. It is only available
on nodes with the KubernetesWorker role.

Change-Id: I5f6269165a81d9a4c4cff48d3ed6b6a55d7f4f46
Reviewed-on: https://review.monogon.dev/c/monogon/+/2861
Tested-by: Jenkins CI
Reviewed-by: Lorenz Brun <lorenz@monogon.tech>
diff --git a/metropolis/node/ports.go b/metropolis/node/ports.go
index 793a68c..ded1815 100644
--- a/metropolis/node/ports.go
+++ b/metropolis/node/ports.go
@@ -63,6 +63,9 @@
 	// proxy for the api-server runs, bound to 127.0.0.1. The metrics
 	// service proxies traffic to it from the public MetricsPort.
 	MetricsKubeAPIServerListenerPort Port = 7845
+	// MetricsContainerdListenerPort is the TCP port on which the
+	// containerd metrics endpoint, bound to 127.0.0.1, is exposed.
+	MetricsContainerdListenerPort Port = 7846
 	// KubernetesAPIPort is the TCP port on which the Kubernetes API is
 	// exposed.
 	KubernetesAPIPort Port = 6443