feat(FormController): add $submitted $setSubmitted

[PatrickJS]

allowing $submitted on FormController allows the user more convenience when dealing with ngMessages for example
https://yearofmoo.github.io/ngMessages/

angular.module('yolo', ['ngMessages'])
.controller('exampleCtrl', function($scope) { 
    this.model = '';
    $scope.submitted = false;
    $scope.submit = function() {
      $scope.submitted = true;
    };
    $scope.interacted = function(field) {
      return $scope.submitted || field.$dirty;
    };
}

<form name="userForm">
  <input name="emailAddress" ng-model="ctrl.model">
  <div 
    ng-messages="userForm.emailAddress.$error" 
    ng-if="interacted(userForm.emailAddress)" 
    ng-messages-include="error-messages"
  ></div>
</form>

with $submitted would simply be

angular.module('yolo', ['ngMessages'])
.controller('exampleCtrl', function($scope) { 
    this.model = '';
}

<form name="userForm">
  <input name="emailAddress" ng-model="ctrl.model">
  <div 
    ng-messages="userForm.emailAddress.$error" 
    ng-if="userForm.$submitted || userForm.emailAddress.$dirty" 
    ng-messages-include="error-messages"
  ></div>
</form>

I can also add .ng-submitted class etc that would help for styles
I also added .ng-submitted to the form for styling input errors when the form is submitted and still dirty

[MehulATL]

this is 💰

[Hendrixer]

can we haz that please?

[rodyhaddad]

Great idea, and we agree it should become a thing.

There's already a PR implementing this feature: #8056 :-)

I'll close this for now, and move the other PR to the current milestone.

[PatrickJS]

sweet