fix(ngModel): use `$evalAsync` for blur events to safely `$apply`

Set the `$touched` asynchronously using `$evalAsync` if the element is blurred during an `$apply`, otherwise it keeps the old behaviour.

Fixes https://github.com/angular/angular.js/issues/8762
@Narretz means `$rootScope.$$phase` (just clearing it up to avoid confusion :smiling_imp:).