22.2.1.4422.

```
create table test_alias (K Int64, D Date, S String, B Int64 Alias length(S)) Engine=MergeTree order by K;
insert into test_alias select number, today(), 'sdfsdfsdfsdfsdfds' from numbers(10000000);

session1: 
clickhouse-benchmark -c 10 <<< "insert into test_alias select number, today(), 'sdfsdfsdfsdfsdfds' from numbers(10000)"

session2: 
alter table test_alias drop column B;
0 rows in set. Elapsed: 251.043 sec.
```

especially it can be a problem with S3 disks

Alias columns do not persist in parts even in columns.txt
{
    if (type == MODIFY_TTL)
        return true;
    if (!ttl || type != MODIFY_COLUMN)
        return false;
    bool ttl_changed = true;
    for (const auto & [name, ttl_ast] : metadata.columns.getColumnTTLs())
    {
        if (name == column_name && queryToString(*ttl) == queryToString(*ttl_ast))
        {
            ttl_changed = false;
            break;
        }
    }
    return ttl_changed;
}
bool AlterCommand::isRemovingProperty() const
{
    return to_remove != RemoveProperty::NO_PROPERTY;
}
std::optional<MutationCommand> AlterCommand::tryConvertToMutationCommand(StorageInMemoryMetadata & metadata, ContextPtr context) const