[ONNX] Reland: Add quantization support to _avg_pool opset 9 and clean up (#81267)
- Add quantization support to _avg_pool opset 9
- Clean up reused / unused variables in avgpool helper
- Add types
- Sort `__all__`
Reland #79793 (Added `argsort` in `__all__`)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/81267
Approved by: https://github.com/BowenBao