feat: implement new handlers for audio, image, embedding, and responses processing

- Added new handlers: AudioHelper, ImageHelper, EmbeddingHelper, and ResponsesHelper to manage respective requests.
- Updated ModelMappedHelper to accept request parameters for better model mapping.
- Enhanced error handling and validation across new handlers to ensure robust request processing.
- Introduced support for new relay formats in relay_info and updated relevant functions accordingly.

controller/channel-test.go

@@ -90,7 +90,7 @@ func testChannel(channel *model.Channel, testModel string) (err error, openAIErr
 
 	info := relaycommon.GenRelayInfo(c)
 
-	err = helper.ModelMappedHelper(c, info)
+	err = helper.ModelMappedHelper(c, info, nil)
 	if err != nil {
 		return err, nil
 	}