[PyTorch] Take advantage of string literals in TORCH_WARN (#54032)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/54032
Add a `const char*` override to c10::Warning::warn so that we can avoid wrapping plain C string literals in std::string.
ghstack-source-id: 125544720
Test Plan: Buildsizebot some iOS apps?
Reviewed By: ezyang
Differential Revision: D27061983
fbshipit-source-id: dc11150c911a4317a8edac75e50c5ba43511ff24
