[package] populate a special attribute on imported modules (#55255)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/55255
This allows packaged code to detect whether or not they are used in a
packaged context, and do different things depending on that. An example
where this might be useful is to control dynamic dependency loading
depending on whether or not something is packaged.
Test Plan: Imported from OSS
Reviewed By: Lilyjjo
Differential Revision: D27544245
Pulled By: suo
fbshipit-source-id: 55d44ef57281524b8d9ab890bd387de97f20bd9f
