This diff introduces adding of the gRPC server empty core implementation using [[ https://github.com/hyperium/tonic | Tonic ]].
The `server` module with the empty API handlers is added (handlers return a "Not implemented yet" error).
Tonic forces us to implement all of the existing handlers in the imported proto file, that's why the deprecated API empty handlers are implemented with the error code "Deprecated". Otherwise, the `cargo build` will fail.
These old API handlers will be removed after removing the old API from a proto file in [[ https://linear.app/comm/issue/ENG-1334/remove-the-old-api-from-the-tunnelbroker-protobuf-file | ENG-1334 ]].
The new API handlers implementations will be added as a follow-up diffs as a handler struct implementation.
Linear task: [[ https://linear.app/comm/issue/ENG-2094/adding-dependencies-and-grpc-tonic-core-in-tunnelbroker-rust | ENG-2094 ]]