Update Argmin/Argmax ONNX Export (#38329)
Summary:
Update Argmin/Argmax ONNX export in opset 12 to export with "select_last_index", and export correctly cases where the same value appears multiple time in the input tensor.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/38329
Reviewed By: hl475
Differential Revision: D21613799
Pulled By: houseroad
fbshipit-source-id: 4597e23561f444c4e56d30c735dae7e9a8a41c5e
