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/sigs.k8s.io/controller-runtime/pkg/reconcile/reconcile.go

@@ -28,6 +28,7 @@ type Result struct {
 	Requeue bool
 
 	// RequeueAfter if greater than 0, tells the Controller to requeue the reconcile key after the Duration.
+	// Implies that Requeue is true, there is no need to set Requeue to true at the same time as RequeueAfter.
 	RequeueAfter time.Duration
 }