[Twig] Move AsTwigFilter/AsTwigFunction attribute rules to the Twig composer-based set

[TomasVotruba]

GetFiltersToAsTwigFilterAttributeRector and GetFunctionsToAsTwigFunctionAttributeRector were registered in the Symfony composer-based set, while both are bound to twig/twig:

public function provideComposerPackageConstraint(): ComposerPackageConstraint
{
    return new ComposerPackageConstraint('twig/twig', '>=3.21');
}

The attributes they add come from Twig itself — Symfony 7.3 only made them usable in Twig extensions. A project on Twig 3.21 without symfony/twig-bundle should still get the rewrite:

 use Twig\Extension\AbstractExtension;
+use Twig\Attribute\AsTwigFunction;

 class SomeExtension extends AbstractExtension
 {
-    public function getFunctions(): array
-    {
-        return [new TwigFunction('some_function', $this->someFunction(...))];
-    }
-
+    #[AsTwigFunction('some_function')]
     public function someFunction(): string
     {
         return 'result';
     }
 }

So both move to config/sets/twig/composer-based.php, under a // twig/twig 3.21 group. No rule behavior changes — the version bond was already correct, only the set registration was in the wrong file.

The rule namespace stays Symfony73 so the classes and their tests stay where they are.