Add manual routing policy for router (#15586)

sgl-model-gateway/benches/request_processing.rs

@@ -67,6 +67,7 @@ fn default_generate_request() -> GenerateRequest {
         return_bytes: false,
         return_entropy: false,
         rid: None,
+        routing_id: None,
     }
 }
 
@@ -122,6 +123,7 @@ fn default_completion_request() -> CompletionRequest {
         return_hidden_states: false,
         sampling_seed: None,
         other: serde_json::Map::new(),
+        routing_id: None,
     }
 }