message: Add input/output index to log messages in PFLR
diff: @@ -566,13 +566,15 @@ Status ProcessFunctionLibraryRuntime::InstantiateMultiDevice(
  VLOG(1) << "Instantiating MultiDevice function \"" << function_name
  << "\" on default device \"" << options.target << "\"";
  if (VLOG_IS_ON(3)) {
  + int index = 0;
  VLOG(3) << "Requested input devices:";
  for (const string& device : options.input_devices) {
  - VLOG(3) << " " << device;
  + VLOG(3) << " " << device << " for input at index " << index++;
  }
  + index = 0;
  VLOG(3) << "Requested output devices:";
  for (const string& device : options.output_devices) {
  - VLOG(3) << " " << device;
  + VLOG(3) << " " << device << " for output at index " << index++;
  }
  }
  