Can users set a fully custom User-Agent that completely replaces the default one, without appending the driver version?

### Use case
Security/compliance policies in some organizations require hiding internal client version information from server logs. Currently there is no way to do this from the client side.

### Describe the solution you'd like
Allow setting a fully custom User-Agent that completely replaces the default one, without appending the driver version.

### Describe the alternatives you've considered
When using the ClickHouse client to send requests to server, the User-Agent header always includes the driver version:User-Agent: ClickHouse-JavaClient/0.6.5 (OpenJDK 64-Bit Server VM/BiSheng_JDK_Enterprise_205.2.0.110.B001; Apache-HttpClient/5.3.4)

Using client_name can only prepend a custom prefix, but the driver version suffix is always appended at the end and cannot be removed.

### Additional context

Commencez par suivre la manière dont le client Java construit l’en-tête User-Agent et dont client_name est appliqué. Vérifiez les tests existants des requêtes du client, puis vérifiez qu’une valeur entièrement personnalisée remplace l’en-tête par défaut sans ajouter la version du pilote.

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