Async API for RestCatalog

### Feature Request / Improvement

RestCatalog currently uses synchronous HTTP calls, while most catalog operations are network io-bound. Native async support would help async consumers and high-concurrency use cases in general.

We could introduce a separate AsyncRestCatalog, preserving the existing synchronous API.

asyncio.to_thread()/running in a dedicated executor is a possible workaround but doesn't give the same benefits as native support as we'd still have the limitations of the sync client (one worker thread per in-flight request being the most annoying in this case).

We can start small without necessarily the full ops coverage, wdyt?

Commencez par l’implémentation existante de RestCatalog et recensez les opérations du catalogue qui utilisent actuellement des appels HTTP synchrones. Définissez le périmètre initial de AsyncRestCatalog tout en préservant l’API synchrone ; l’issue laisse ouverts la couverture exacte des opérations et l’approche de validation.

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