**Describe the bug**
The ClickHouse client freezes when executing `ALTER TABLE` with `ADD COLUMN` and `MODIFY ORDER` on a table built using Replicated Versioned Collapsing Merge Tree engine.

**How to reproduce**
* ClickHouse client version 20.10.1.1.
Connecting to localhost:9000 as user default.
Connected to ClickHouse server version 20.10.1 revision 54440.

* `CREATE TABLE` statements
```
SHOW CREATE TABLE table0

┌─statement──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│ CREATE TABLE default.table0
(
    `d` Date,
    `a` String,
    `b` UInt8,
    `x` String,
    `y` Int8,
    `version` UInt64,
    `sign` Int8 DEFAULT 1
)
ENGINE = ReplicatedVersionedCollapsingMergeTree('/clickhouse/tables/{shard}/table0', '{replica}', sign, version)
PARTITION BY y
ORDER BY d
SETTINGS index_granularity = 8192 │
└────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

1 rows in set. Elapsed: 0.004 sec.
```

* Queries to run that lead to unexpected result
```
ALTER TABLE table0 ADD COLUMN order UInt32, MODIFY ORDER BY (d, order)
```
for (const auto & part : parts_to_remove)
        {
            LOG_INFO(log, "Detaching {}", part->relative_path);
            part->makeCloneInDetached("", metadata_snapshot);
        }
    }
    
    tryRemovePartsFromZooKeeperWithRetries(parts_to_remove);
    if (entry.detach)
        LOG_DEBUG(log, "Detached {} parts inside {}.", parts_to_remove.size(), entry.new_part_name);
    else
        LOG_DEBUG(log, "Removed {} parts inside {}.", parts_to_remove.size(), entry.new_part_name);
    
    
    parts_to_remove.clear();
    cleanup_thread.wakeup();
}
bool StorageReplicatedMergeTree::executeReplaceRange(const LogEntry & entry)
{
    Stopwatch watch;
    auto & entry_replace = *entry.replace_range_entry;
    auto metadata_snapshot = getInMemoryMetadataPtr();
    MergeTreePartInfo drop_range = MergeTreePartInfo::fromPartName(entry_replace.drop_range_part_name, format_version);
    
    bool replace = drop_range.getBlocksCount() > 1;
    queue.removePartProducingOpsInRange(getZooKeeper(), drop_range, entry);
    struct PartDescription
    {
        PartDescription(size_t index_, const String & src_part_name_, const String & new_part_name_, const String & checksum_hex_,