Use patch instead of update to alleviate HRA conflict on webhook (#358)

We sometimes see that integration test fails due to runner replicas not meeting the expected number in a timely manner. After investigating a bit, this turned out to be due to that HRA updates on webhook-based autoscaler and HRA controller are conflicting. This changes the controllers to use Patch instead of Update to make conflicts less likely to happen.

I have also updated the hra controller to use Patch when updating RunnerDeployment, too.

Overall, these changes should make the webhook-based autoscaling more reliable due to less conflicts.

controllers/horizontal_runner_autoscaler_webhook.go

@@ -371,8 +371,6 @@ func (autoscaler *HorizontalRunnerAutoscalerGitHubWebhook) tryScaleUp(ctx contex
 		return nil
 	}
 
-	log := autoscaler.Log.WithValues("horizontalrunnerautoscaler", target.HorizontalRunnerAutoscaler.Name)
-
 	copy := target.HorizontalRunnerAutoscaler.DeepCopy()
 
 	amount := 1
@@ -388,10 +386,8 @@ func (autoscaler *HorizontalRunnerAutoscalerGitHubWebhook) tryScaleUp(ctx contex
 		Replicas:       amount,
 	})
 
-	if err := autoscaler.Client.Update(ctx, copy); err != nil {
-		log.Error(err, "Failed to update horizontalrunnerautoscaler resource")
-
-		return err
+	if err := autoscaler.Client.Patch(ctx, copy, client.MergeFrom(&target.HorizontalRunnerAutoscaler)); err != nil {
+		return fmt.Errorf("patching horizontalrunnerautoscaler to add capacity reservation: %w", err)
 	}
 
 	return nil