For some reasons when we delete a MergeTree Part in atomic way something may go wrong - and leave the `delete_tmp_*` folder or it's part on disk. This may lead to a disk space consumption over time.

It's suggested to delete this folders at least at server start-up. Current solution with `clearOldTemporaryDirectories()` doesn't work because this method is called periodically from a thread without any locks or advisory on folders - it may cause the race conditions.
{
        for (size_t thread = 0; thread < num_threads; ++thread)
        {
            pool.scheduleOrThrowOnError([&, thread]
            {
                while (true)
                {
                    std::pair<String, DiskPtr> thread_part;
                    {
                        const std::lock_guard lock{part_select_mutex};
                        if (remaining_thread_parts.empty())
                            return;
                        
                        auto thread_idx = thread;
                        if (threads_parts[thread].empty())
                        {
                            
                            std::uniform_int_distribution<size_t> distribution(0, remaining_thread_parts.size() - 1);
                            auto it = remaining_thread_parts.begin();
                            std::advance(it, distribution(thread_local_rng));
                            thread_idx = *it;
                        }
                        auto & thread_parts = threads_parts[thread_idx];
                        thread_part = thread_parts.back();
                        thread_parts.pop_back();
                        if (thread_parts.empty())
                            remaining_thread_parts.erase(thread_idx);
                    }
                    load_part(thread_part.first, thread_part.second);
                }