[ONNX] Introduce 'Functionalization' for fx exporter (#98245)
<img src="https://user-images.githubusercontent.com/9376104/229648898-7e85efc8-143f-42f9-93e0-298a8f86c0a1.png" width="80%" height="80%">
Pull Request resolved: https://github.com/pytorch/pytorch/pull/98245
Approved by: https://github.com/wschin, https://github.com/titaiwangms
