m/n/kubernetes: introduce feature gate infra

This introduces centralized infrastructure to control feature gates in K8s.

It includes a test to make sure that we do not keep outdated flags in there.

Change-Id: Ife251cbd5210bc8b3757bb3829e91bcdb2e6fdfb
Reviewed-on: https://review.monogon.dev/c/monogon/+/3664
Reviewed-by: Tim Windelschmidt <tim@monogon.tech>
Tested-by: Jenkins CI
diff --git a/metropolis/node/kubernetes/kubelet.go b/metropolis/node/kubernetes/kubelet.go
index 2c46080..9845b3b 100644
--- a/metropolis/node/kubernetes/kubelet.go
+++ b/metropolis/node/kubernetes/kubelet.go
@@ -118,8 +118,9 @@
 		VolumePluginDir: s.EphemeralDirectory.FlexvolumePlugins.FullPath(),
 		// Currently we allocate a /24 per node, so we can have a maximum of
 		// 253 pods per node.
-		MaxPods:    253,
-		PodLogsDir: "/data/kubelet/logs",
+		MaxPods:      253,
+		PodLogsDir:   "/data/kubelet/logs",
+		FeatureGates: extraFeatureGates.AsMap(),
 	}
 }