fix(input[number]): validate min/max against viewValue

This brings the validation in line with HTML5 validation, i.e. what the user has entered
is validated, and not a possibly transformed value.

Fixes #12761
Closes #16325

BREAKING CHANGE

`input[type=number]` with `ngModel` now validates the input for the `max`/`min` restriction against
the `ngModelController.$viewValue` instead of against the `ngModelController.$modelValue`.

This affects apps that use `$parsers` or `$formatters` to transform the input / model value.

If you rely on the $modelValue validation, you can overwrite the `min`/`max` validator from a custom directive, as seen in the following example directive definition object:

```
{
  restrict: 'A',
  require: 'ngModel',
  link: function(scope, element, attrs, ctrl) {
    var maxValidator = ctrl.$validators.max;

    ctrk.$validators.max = function(modelValue, viewValue) {
      return maxValidator(modelValue, modelValue);
    };
  }
}
```