[special] Alias for sigmoid and logit & follow-up (#54759)
Summary:
Reference: https://github.com/pytorch/pytorch/issues/50345
Chages:
* Alias for sigmoid and logit
* Adds out variant for C++ API
* Updates docs to link back to `special` documentation
Pull Request resolved: https://github.com/pytorch/pytorch/pull/54759
Reviewed By: mrshenli
Differential Revision: D27615208
Pulled By: mruberry
fbshipit-source-id: 8bba908d1bea246e4aa9dbadb6951339af353556
