Adds multiply and divide aliases (#44463)
Summary:
These alias are consistent with NumPy. Note that C++'s naming would be different (std::multiplies and std::divides), and that PyTorch's existing names (mul and div) are consistent with Python's dunders.
This also improves the instructions for adding an alias to clarify that dispatch keys should be removed when copying native_function.yaml entries to create the alias entries.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/44463
Reviewed By: ngimel
Differential Revision: D23670782
Pulled By: mruberry
fbshipit-source-id: 9f1bdf8ff447abc624ff9e9be7ac600f98340ac4
