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.
std::shared_ptr<MergeMutateSelectedEntry> merge_mutate_entry;
    {
        std::unique_lock lock(currently_processing_in_background_mutex);
        if (merger_mutator.merges_blocker.isCancelled())
            throw Exception("Cancelled merging parts", ErrorCodes::ABORTED);
        merge_mutate_entry = selectPartsToMerge(
            metadata_snapshot,
            aggressive,
            partition_id,
            final,
            out_disable_reason,
            table_lock_holder,
            lock,
            txn,
            optimize_skip_merged_partitions,
            &select_decision);
    }
    
    if (select_decision == SelectPartsDecision::NOTHING_TO_MERGE)
        return true;
    if (!merge_mutate_entry)
        return false;
    
    auto task = std::make_shared<MergePlainMergeTreeTask>(
        *this, metadata_snapshot, deduplicate, deduplicate_by_columns, merge_mutate_entry, table_lock_holder, [](bool){});
    task->setCurrentTransaction(MergeTreeTransactionHolder{}, MergeTreeTransactionPtr{txn});
    executeHere(task);
    return true;
}
bool StorageMergeTree::partIsAssignedToBackgroundOperation(const DataPartPtr & part) const