[TP] Add deprecation warnings in the documentations for Pairwise parallel, sequence parallel and other prepare input/output functions (#111176)
As part of TP UX improvements, we want to keep our API simple (not easy) so that users get the flexibility to do what they want and avoid a too generic API which tries to solve everything and get things too complicated. We are updating the doc accordingly.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/111176
Approved by: https://github.com/wanchaol
ghstack dependencies: #111160, #111166
