cmd/k8s-operator: configure proxies for HA Ingress to run in cert share mode (#15308)

cmd/k8s-operator: configure HA Ingress replicas to share certs

Creates TLS certs Secret and RBAC that allows HA Ingress replicas
to read/write to the Secret.
Configures HA Ingress replicas to run in read-only mode.

Updates tailscale/corp#24795


Signed-off-by: Irbe Krumina <irbe@tailscale.com>

cmd/k8s-operator/operator_test.go

@@ -1387,10 +1387,10 @@ func Test_serviceHandlerForIngress(t *testing.T) {
 			Name:      "headless-1",
 			Namespace: "tailscale",
 			Labels: map[string]string{
-				LabelManaged:         "true",
-				LabelParentName:      "ing-1",
-				LabelParentNamespace: "ns-1",
-				LabelParentType:      "ingress",
+				kubetypes.LabelManaged: "true",
+				LabelParentName:        "ing-1",
+				LabelParentNamespace:   "ns-1",
+				LabelParentType:        "ingress",
 			},
 		},
 	}