ONNX Export Slice and Flip ops for opset 10
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/20533
Reviewed By: zrphercule
Differential Revision: D15579713
Pulled By: houseroad
fbshipit-source-id: 91f3ac0cb14ef226f980362b0013b6b92cb8b8da
