use istio client-go library instead of knative (#1661)

use istio client-go library instead of knative
bump kubernetes dependency version
change code coverage to codecov

vendor/k8s.io/client-go/rest/zz_generated.deepcopy.go

@@ -38,6 +38,11 @@ func (in *TLSClientConfig) DeepCopyInto(out *TLSClientConfig) {
 		*out = make([]byte, len(*in))
 		copy(*out, *in)
 	}
+	if in.NextProtos != nil {
+		in, out := &in.NextProtos, &out.NextProtos
+		*out = make([]string, len(*in))
+		copy(*out, *in)
+	}
 	return
 }