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.
reserved_space
                = storage.tryReserveSpacePreferringTTLRules(metadata_snapshot, total_size, ttl_infos, time(nullptr), max_volume_index);
    }
    if (!reserved_space)
    {
        if (is_mutation)
            throw Exception("Not enough space for mutating part '" + future_part->parts[0]->name + "'", ErrorCodes::NOT_ENOUGH_SPACE);
        else
            throw Exception("Not enough space for merging parts", ErrorCodes::NOT_ENOUGH_SPACE);
    }
    future_part->updatePath(storage, reserved_space.get());
    for (const auto & part : future_part->parts)
    {
        if (storage.currently_merging_mutating_parts.contains(part))
            throw Exception("Tagging already tagged part " + part->name + ". This is a bug.", ErrorCodes::LOGICAL_ERROR);
    }
    storage.currently_merging_mutating_parts.insert(future_part->parts.begin(), future_part->parts.end());
}
CurrentlyMergingPartsTagger::~CurrentlyMergingPartsTagger()
{
    std::lock_guard lock(storage.currently_processing_in_background_mutex);
    for (const auto & part : future_part->parts)
    {
        if (!storage.currently_merging_mutating_parts.contains(part))
            std::terminate();
        storage.currently_merging_mutating_parts.erase(part);
    }
    storage.currently_processing_in_background_condition.notify_all();
}
Int64 StorageMergeTree::startMutation(const MutationCommands & commands, ContextPtr query_context)