Support extra files in _load_for_mobile (#47425)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/47425
Extra files can be exported in lite interpreter model, but it could not be loaded. This PR is to add the capability to load extra files from lite interpreter model. Because extra_files is a default argument, it should not affect the existing usage of _load_for_mobile. It's a simple assembly or a generic unordered_map. No additional dependency should be introduced and the size overhead should be small (to be tested).
Test Plan: Imported from OSS
Reviewed By: kwanmacher
Differential Revision: D24770266
Pulled By: iseeyuan
fbshipit-source-id: 7e8bd301ce734dbbf36ae56c9decb045aeb801ce
