[tunnelbroker-client] Creating a Cargo project file

Summary:
This diff introduces the creation of the Cargo project file for the tunnelbroker-client shared library.
This library would be used as a Tunnelbroker client library based on Tonic in a keyserver using the NAPI-RS bridge and in the native later using the CXX bridge.

Following dependencies were added:

• anyhow: Using for easy passing Rust Result;
• tokio: Used for creating runtime for the Tokio in D6281;
• tonic: gRPC client used in D6281 and beyond;
• prost and tonic-build: Dependency for the protobuf compilation in D6279;
• lazy_static: Used for the lazy tokio runtime initialization in D6281;
• tracing: We are using the tracing crate for better logging in the tokio threads;
• futures, futures_utils: Is used in the D6284 for easy use of Tonic streams.

Linear task: ENG-2728

Test Plan: To build the project patch to the D6281 and run nix develop --accept-flake-config -c bash -c "cargo test"

Reviewers: jon, bartek, tomek, ashoat

Reviewed By: jon, bartek, tomek, ashoat

Subscribers: ashoat, tomek, atul

Differential Revision: https://phab.comm.dev/D6277