[DependencyInjection] Cover adding dependency into existing constructor

[TomasVotruba]

Adds a fixture for GetBySymfonyStringToConstructorInjectionRector covering the case where the class already has a constructor with a promoted param - the new dependency is appended to it instead of a fresh constructor being created.

This edge previously lived only in rector-src tests/Issues/AddClassDependency; moving it next to the rule where it belongs.

 final class StickWithConstructor extends Controller
 {
     public function __construct(
-        private readonly EventDispatcherInterface $eventDispatcher,
+        private readonly EventDispatcherInterface $eventDispatcher, private readonly \Symfony\Component\Validator\Validator\ValidatorInterface $validator,
     ) {
     }

     public function configure()
     {
-        $someType = $this->get('validator');
+        $someType = $this->validator;
     }
 }