Merge the ParamConverters on class level and the ParamConverters in method level

I have the following controller:

```
/**
 * Location controller.
 *
 * @Route("/approve/period/{period_id}", requirements={"period_id":"\d+"})
 * @ParamConverter("period", options={"id"="period_id"})
 */
class ApprovementController extends Controller
{

    /**
     * @Route("/department/{department_id}/approve", name="something", requirements={"department_id":"\d+"}, defaults={"_format":"json"}, options={"expose":true})
     * @ParamConverter("department", options={"id"="department_id"})
     */
    public function approveDayAction(Department $department, Period $period)
    {
        [...]
    }
}
```

The problem here is that due to the way the annotations are merged, the ParamConverter on class level was dropped, and overridden by that on method level, instead of merged into it's array.

As a workaround, I had to copy the class level annotation to the method level annotation