Add Cargo manifest, headers, and Rust linkings to the `CMakeLists` file to build the Rust library.
An empty `services/tunnelbroker/rust/src/lib.rs` file was added to prevent build failing. This file will containts the Rust library code.
Linear task: [[ https://linear.app/comm/issue/ENG-1330/rust-notification-library-integration | ENG-1330 ]]