Fix clip_grad_norm_ / clip_grad_value_ to take input by value instead of by non-const ref (#30216)
Summary:
The original design of `torch::nn::utils::clip_grad_norm_` / `clip_grad_value_` takes input by non-const reference, which prevents users from passing rvalue reference as input into the functions. This PR changes the functions to take input by value, which matches the Python version's semantics, and also adheres to the C++ API convention that if a function modifies its input in-place, it should take that input by value.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/30216
Differential Revision: D18632543
Pulled By: yf225
fbshipit-source-id: 97a09d6467f982fe9c8120f483a9c07fcf13699e
