Add sample validation for LKJCholesky.log_prob (#52763)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/52724.
This fixes the following for the LKJCholesky distribution in master:
- `log_prob` does sample validation when `validate_args=True`.
- exposes documentation for the LKJCholesky distribution.
cc. fehiepsi, fritzo
Pull Request resolved: https://github.com/pytorch/pytorch/pull/52763
Reviewed By: anjali411
Differential Revision: D26657216
Pulled By: neerajprad
fbshipit-source-id: 12e8f8384cf0c3df8a29564c1e1718d2d6a5833f
