Implement func createOrUpdateZPostgresql like the other peripheral resources

[LimKianAn]

zalando.Postgresql was the first peripheral resources we implemented. The logic of its creation and update scattered in func Reconcile. This chaos slows down the development speed and seems odd as compared with other peripheral resources. Moreover, there was a bug in the old func createZalandoPostgresql which returns ctrl.Resul{}, nil and finishes the reconciliation. After the implementation, now we have a clear workflow in func Reconcile:

	// Check if zalando dependencies are installed. If not, install them.
	if err := r.ensureZalandoDependencies(ctx, instance); err != nil {
		return ctrl.Result{}, fmt.Errorf("error while ensuring Zalando dependencies: %v", err)
	}

	if err := r.createOrUpdateZalandoPostgresql(ctx, instance, log); err != nil {
		return ctrl.Result{}, fmt.Errorf("failed to create or update zalando postgresql: %w", err)
	}

	if err := r.CreateSvcLBIfNone(ctx, instance); err != nil {
		return ctrl.Result{}, err
	}

	// Check if socket port is ready
	port := instance.Status.Socket.Port
	if port == 0 {
		log.Info("socket port not ready")
		return ctrl.Result{Requeue: true}, nil
	}

	// Update status will be handled by the StatusReconciler, based on the Zalando Status
	if err := r.createOrUpdateCWNP(ctx, instance, int(port)); err != nil {
		return ctrl.Result{}, fmt.Errorf("unable to create or update corresponding CRD ClusterwideNetworkPolicy: %W", err)
	}

[eberlep]

Looks alright