[ONNX] Support one_hot (#34454)
Summary:
This PR resolves https://github.com/pytorch/pytorch/issues/22534 by adding a converter for the `torch.nn.functional.one_hot` function, and covering it with a test.
Are there other places this should be tested?
Pull Request resolved: https://github.com/pytorch/pytorch/pull/34454
Reviewed By: hl475
Differential Revision: D20354255
Pulled By: houseroad
fbshipit-source-id: 84224c1610b2cc7986c91441c65647ddc090750d
