[services] Tunnelbroker - Add Cargo manifest, headers and Rust linking to the CMakeLists

Summary:
Add Cargo manifest, headers, and Rust linkings to the CMakeLists file to build the Rust library.

Linear task: ENG-1330

Test Plan: Running build using the standard command yarn run-tunnelbroker-service successfully built an empty rust library and link it to the CMake project.

Reviewers: varun, palys-swm, karol-bisztyga, jonringer-comm

Reviewed By: varun, jonringer-comm

Subscribers: jonringer-comm, ashoat, palys-swm, Adrian, atul, karol-bisztyga, yayabosh

Differential Revision: https://phab.comm.dev/D4537