[Native] Update native_rust_library ffi to reflect client gRPC

Summary:
Update ffi to avoid merge conflicts between varun and I.

https://linear.app/comm/issue/ENG-3385

Test Plan:

cd native/native_rust_library
cargo build

Android build gate

Reviewers: ashoat, varun, bartek

Reviewed By: varun

Subscribers: tomek, atul

Differential Revision: https://phab.comm.dev/D7198