Allow torch.utils.cpp_extension.load to load shared libraries that aren't Python...

Allow torch.utils.cpp_extension.load to load shared libraries that aren't Python modules (#13941)

Summary:
For custom TorchScript operators, `torch.ops.load_library` must be used and passed the path to the shared library containing the custom ops. Our C++ extensions stuff generally is meant to build a Python module and import it. This PR changes `torch.utils.cpp_extension.load` to have an option to just return the shared library path instead of importing it as a Python module, so you can then pass it to `torch.ops.load_library`. This means folks can re-use `torch.utils.cpp_extension.load` and `torch.utils.cpp_extension.load_inline` to even write their custom ops inline. I think t-vi  and fmassa will appreciate this.

soumith
Pull Request resolved: https://github.com/pytorch/pytorch/pull/13941

Differential Revision: D13110592

Pulled By: goldsborough

fbshipit-source-id: 37756307dbf80a81d2ed550e67c8743dca01dc20