Hook to store additional metadata about environment (#20863)
Summary:
In larger system environment, there's usually a need to store some information about how the model was created (e.g. from which process, workflow, by which user, etc). It's almost like JPEG metadata written by camera.
This PR adds a low-level c++ hook to allow population of additional files in zip container based on environment. The reason to have it a low-level hook instead of top-level API wrapper (e.g. `m.save_with_metadata`) is to capture all usages of the saving API transparently for user.
Let me know if there are concerns.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20863
Differential Revision: D15487941
Pulled By: dzhulgakov
fbshipit-source-id: 120c5a4c9758aa82846bb51a1207f923e3da1333
