Enable export in external data format with ppe.onnx

[linshokaku]

In ppe.onnx, the destination for model output is specified by a file pointer when exporting onnx, but with torch>=1.11 onwards, along with the deprecation of the use_external_data flag, functionality has been added to output external data in the parent directory by specifying a file path when the model size exceeds a certain size. We will make modifications to be able to utilize this.