This diff introduces adding the helper method to the Commtest integration API tests with the gRPC client to call the `NewSession` [[ https://github.com/CommE2E/comm/blob/40eb1354aa060a1c82282a21d89d8eb2a40bc3ab/shared/protos/tunnelbroker.proto#L9 | request ]] to the Tunnelbroker server.
Linear task: [[ https://linear.app/comm/issue/ENG-1657 | ENG-1657 ]]