Add warning for list_files function and related

## What problem would the enhancement address for VIP?

I've recently been doing a code review and noticed the `list_files` function had no warning attached. On VIP Filesystem, the `list_files`, `scandir`, `opendir` will return empty result sets or false, so we should probably highlight this to customers to avoid unexpected results.

## Describe the solution you'd like
A warning should be added when the following functions are coded:
- list_files - WP
- scandir - PHP
- opendir - PHP

## What code should be reported as a violation?

```
$files = list_files( $folder, 2 );
```

## What code should *not* be reported as a violation?

## Additional context

Repérez les règles PHP_CodeSniffer existantes pour les vérifications de fonctions propres à WordPress et à VIP, puis examinez la manière dont les avertissements sont définis et testés. Confirmez le comportement attendu des avertissements pour list_files, scandir et opendir, y compris l’exemple list_files fourni ; le travail est terminé lorsque ces appels sont signalés de manière cohérente.

Rédigé par le modèle d'indexation à partir du texte de l'issue.