[testing] OpInfo for sgn and sign (#53885)
Summary:
Reference https://github.com/pytorch/pytorch/issues/42515
TODO:
* [x] Check rendered docs. https://11525594-65600975-gh.circle-artifacts.com/0/docs/generated/torch.sgn.html
Pull Request resolved: https://github.com/pytorch/pytorch/pull/53885
Reviewed By: ejguan
Differential Revision: D27114318
Pulled By: mruberry
fbshipit-source-id: 678179d87741aacd3b50f03dc460207c5aa29589
