feat(k8s): Add a port name to service definition (#2933)

It should cover this issue:  https://github.com/woodpecker-ci/woodpecker/issues/2931

To sum up, when several ports need to be specified, they must be named

pipeline/backend/kubernetes/service_test.go

@@ -32,14 +32,17 @@ func TestService(t *testing.T) {
 	  "spec": {
 	    "ports": [
 	      {
+	        "name": "port-1",
 	        "port": 1,
 	        "targetPort": 1
 	      },
 	      {
+	        "name": "port-2",
 	        "port": 2,
 	        "targetPort": 2
 	      },
 	      {
+	        "name": "port-3",
 	        "port": 3,
 	        "targetPort": 3
 	      }