[Redo] Enhance fakepg: alltoall and alltoall_base (#107798)
[ghstack-poisoned]
Redo https://github.com/pytorch/pytorch/pull/107624, previously tried to land via `ghstack land`, but that doesn't work with pytorch repo which has protected main branch. As a result, that PR was only merged to [gh/xmfan/1/base](https://github.com/pytorch/pytorch/tree/gh/xmfan/1/base).
This PR manually merges [gh/xmfan/1/base](https://github.com/pytorch/pytorch/tree/gh/xmfan/1/base) into main, via pytorchbot
Pull Request resolved: https://github.com/pytorch/pytorch/pull/107798
Approved by: https://github.com/wanchaol, https://github.com/fduwjj
