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

[Gasoonjia]

#12839 is working on this;
currently working on some dependency issue: ImportError: /opt/conda/envs/py_3.10/lib/python3.10/site-packages/executorch/extension/pybindings/_portable_lib.cpython-310-x86_64-linux-gnu.so: undefined symbol: _ZN10executorch9extension14bundled_module13BundledModule7executeERKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEm