Add `torch.atleast_{1d/2d/3d}` (#41317)
Summary:
https://github.com/pytorch/pytorch/issues/38349
TODO:
* [x] Docs
* [x] Tests
Pull Request resolved: https://github.com/pytorch/pytorch/pull/41317
Reviewed By: ngimel
Differential Revision: D22575456
Pulled By: mruberry
fbshipit-source-id: cc79f4cd2ca4164108ed731c33cf140a4d1c9dd8
