Expose intended public constraints. Fixes #106386 (#106458)
Fixes #106386
Straightforward change, just exposes the `one_hot` and `nonnegative` distribution constraints that are intended to be public. This fixes downstream pyro usage of these constraints.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/106458
Approved by: https://github.com/ezyang, https://github.com/kit1980
