Exposes _aminmax as aminmax and makes it structured (#62401)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/62401
This PR exposes the `torch._aminmax` operator as `torch.aminmax`.
**TODO**
- [x] add examples to documentation
- [x] add minmax to rst docs
fixes https://github.com/pytorch/pytorch/issues/62164
Test Plan: Imported from OSS
Reviewed By: soulitzer
Differential Revision: D30072246
Pulled By: heitorschueroff
fbshipit-source-id: 557d30af7c28ca6c238c59122367104036429ecd
