Lazy `sycl::queue` creation in oneDPL hetero policies

[SergeyKopienko]

Attention: ABI breaking change.

Yet another approach to lazy sycl::queue creation in oneDPL hetero policies:

• the source issue described at https://github.com/oneapi-src/oneDPL/issues/1060
• the previous approach has been implemented by @adamfidel in the PR https://github.com/oneapi-src/oneDPL/pull/1154

The main implementation detail is std::once_flag and ::std::call_once usage packed into separate container

template <class TSYCLQueueFactory>
class sycl_queue_container
{
  public:
    template <typename... Args>
    sycl::queue
    get_queue(Args&&... args)
    {
        ::std::call_once(__is_created, [&]() {
            TSYCLQueueFactory factory;
            __queue.emplace(factory(::std::forward<Args>(args)...));
        });

        assert(__queue.has_value());
        return __queue.value();
    }

  private:
    ::std::once_flag __is_created;
    ::std::optional<sycl::queue> __queue;
};

This container shares between hetero policies instances:

template <typename TFactory>
using sycl_queue_container_ptr = ::std::shared_ptr<sycl_queue_container<TFactory>>;


// ...


template <typename KernelName = DefaultKernelName, class TSyclQueueFactory = TDefaultSYCLQueueFactory>
class device_policy
{
  public:
    // ...

  private:
    mutable sycl_queue_container_ptr<TSyclQueueFactory> q_container;       // <<<<<<-- shared sycl::queue container
};

From my point of view this approach is correct because it's simple repeat something like sycl::queue implementation (pimpl-implementation) and we don't introduce any new synchronization errors here.