[native] add CommRustModule bindings for registerWalletUser

Summary:
These bindings will be used by the native IdentityServiceContextProvider in the subsequent diff

Depends on D11080

Test Plan: successfully built app for iOS simulator

Reviewers: kamil, bartek

Reviewed By: kamil, bartek

Subscribers: kamil, bartek, tomek

Differential Revision: https://phab.comm.dev/D11081