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
Thanks for the clarification @gkalpak Why $rootScope is explained here: https://github.com/angular/angular.js/pull/8849#issue-41537374