Summary:
1. is to convert Function -> mobile::Function
2. is to serialize mobile::Function
This also opens opportunity to create mobile::Module without saving/reloading
Fixes #{issue number}
Pull Request resolved: https://github.com/pytorch/pytorch/pull/66494
Reviewed By: zhxchen17
Differential Revision: D32293022
Pulled By: qihqi
fbshipit-source-id: 29b43d47ff86071d5e2f9d6ca4dba4445711ce3d
