Migrate Pybindings to Module API

[lucylq]

Currently, Pybindings uses a PyModule data structure under the hood. We can replace this with the Module API to:

• avoid maintaining two similar classes
• get new features in Module for free (eg. program-data separation)

cc @larryliu0820 @JacobSzwejbka

[JacobSzwejbka]

@Conarnar is working on adding support for Program, and potentially Method. I think @Gasoonjia is working on this directly though