Function run_rpc_listener 

async fn run_rpc_listener<R: Runtime>(
    runtime: R,
    incoming: impl Stream<Item = Result<(Stream, SocketAddr, Arc<RpcConnInfo>)>> + Unpin,
    rpc_mgr: Arc<RpcMgr>,
    client: TorClient<R>,
    rpc_state: Arc<RpcVisibleArtiState>,
) -> Result<()>

Backend function to implement an RPC listener: runs in a loop.