[ResourceBundle] Resource choice form type

| Q             | A
| ------------- | ---
| Bug fix?      | [no]
| New feature?  | [yes]
| BC breaks?    | [no]
| Deprecations? | [no]
| Tests pass?   | [yes]
| Fixed tickets | [ #1384 ]
| License       | MIT
| Doc PR        | []

I use this form type in my project. But it can be usefull here too. But this form type is container aware, is there other way to get class names by resource name?
```php
if (isset($this->classes[model][$resourceName])) {
 return $this->classes[model][$resourceName]
}

throw new InvalidConfigurationException(sprintf('Unknown resource "%s"', $resourceName));
```
This should be better, no ?