[ONNX] Use onnxruntime to run fx tests (#94638)
- Enable the mnist test
- Removed `max_pool2d` in the test because we don't have the op yet.
- Add aten::convolution
- Bump onnxscript version
Pull Request resolved: https://github.com/pytorch/pytorch/pull/94638
Approved by: https://github.com/BowenBao, https://github.com/wschin, https://github.com/titaiwangms
