refactor: Simplify OpenAI handler function signature and remove unused TextResponseWithError struct; introduce common_handler for rerank functionality

relay/channel/vertex/adaptor.go

@@ -178,7 +178,7 @@ func (a *Adaptor) DoResponse(c *gin.Context, resp *http.Response, info *relaycom
 		case RequestModeGemini:
 			err, usage = gemini.GeminiChatHandler(c, resp, info)
 		case RequestModeLlama:
-			err, usage = openai.OpenaiHandler(c, resp, info.PromptTokens, info.OriginModelName)
+			err, usage = openai.OpenaiHandler(c, resp, info)
 		}
 	}
 	return