Method SocketTask

mlx/distributed/ring/ring.cpp:155–156

 private:
  struct SocketTask {
    SocketTask(void* b, size_t s, std::promise<void>&& p)
        : buffer(b), size(s), promise(std::move(p)) {}
    SocketTask(SocketTask&& t)
        : buffer(t.buffer), size(t.size), promise(std::move(t.promise)) {}
    void* buffer;