This diff introduces the `get_new_session_id` internal function which is a gRPC unary request to the Tunnelbroker server to [[ https://www.notion.so/commapp/Tunnelbroker-028bdd578e4c487fb570dbb862952ec6#711c4d2083a54263a983aa0bd1b54c5d | create a new session ]] and obtain a `SessionID`. The function gets the pointer to the Tonic client, and new session parameters (including signed nonce from the D6039, D5999), and returns the `sessionID` from the server.
Linear task: [[ https://linear.app/comm/issue/ENG-2434/implement-new-session-grpc-methods-in-rust-for-the-native-client | ENG-2434 ]]