title: How to user updateOn blur in FormBuilder
body: <p>I have a custom async validator, and I want to set <code>updateOn: 'blur'</code> property using <code>FormBuilder</code>:</p>
  
  <pre><code>myForm = this.formBuilder.group({
     email: ['', [Validators.required], [this.myAsyncValidator]]
     // ...
  });
  </code></pre>
  
  <p>I tried this but it does not work:</p>
  
  <pre><code>email: ['', [Validators.required], [this.myAsyncValidator, {updateOn: 'blur'}]]
  </code></pre>
  
  <p><strong>Note</strong></p>
  
  <p>I DO NOT want to create form control instances manually like the following:</p>
  
  <pre><code>myForm = new FormGroup({
      email: new FormControl('', {asyncValidators: [this.myAsyncValidator]}, updateOn: 'blur')
  });
  </code></pre>