Method detect_destruct

tests/BS_thread_pool_test.cpp:2619–2622

{
public:
    explicit detect_destruct(std::atomic<bool>* object_exists_) : object_exists(object_exists_)
    {
        *object_exists = true;
    };

    detect_destruct(const detect_destruct&) = delete;
    detect_destruct(detect_destruct&&) noexcept = delete;