Document monitored barrier (#58322)
Summary:
Will not land before the release, but would be good to have this function documented in master for its use in distributed debugability.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/58322
Reviewed By: SciPioneer
Differential Revision: D28595405
Pulled By: rohan-varma
fbshipit-source-id: fb00fa22fbe97a38c396eae98a904d1c4fb636fa
