cauchy_ few fixes (1) check gamma > 0 (2) better dtype error log (#93314)
Related #92047
(1) `torch.Tensor.cauchy_` is missing check for `gamma > 0` (`torch.distributions.cauchy.Cauchy` correctly checks `gamma > 0`).
(2) add better error log on dtype similar to exponential_
Pull Request resolved: https://github.com/pytorch/pytorch/pull/93314
Approved by: https://github.com/jgong5, https://github.com/fritzo, https://github.com/lezcano
