Function connect 

pub async fn connect<S, C>(
    server: S,
    client: C,
) -> Result<(RunningService<RoleServer, S>, RunningService<RoleClient, C>), ConnectError>
where
    S: Service<RoleServer>,
    C: Service<RoleClient>,

Helper function to connect an MCP server and client via in-memory transport This handles the initialization handshake by running both concurrently