[native] generate C++ spec for CommRustModule

Summary:
ENG-4232

Creating a separate module for Rust API. This is a part of CommCoreModule refactor.

Make codegen generate C++ for module.

Depends on D8655

Test Plan: run codegen-jsi

Reviewers: bartek, michal, tomek, varun

Reviewed By: bartek

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D8656