
**Bug description**
Unlike `cluster()`, `clusterAllReplicas()` does not implement `_shard_num`. 

I would expect
```
SELECT _shard_num
FROM clusterAllReplicas(prod, system.one)
ORDER BY _shard_num ASC
FORMAT PrettyCompactMonoBlock

┌─_shard_num─┐
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
└────────────┘
```
to have an output more useful like
```
SELECT _shard_num
FROM cluster(prod, system.one)
ORDER BY _shard_num ASC
FORMAT PrettyCompactMonoBlock

┌─_shard_num─┐
│          1 │
│          2 │
│          3 │
│          4 │
│          5 │
│          6 │
│          7 │
│          8 │
│          9 │
│         10 │
│         11 │
│         12 │
│         13 │
│         14 │
│         15 │
└────────────┘
```

**Releases where this has been tested**

* v20.3.12.112-stable

**References**

[cluster, clusterAllReplicas documentation](https://clickhouse.tech/docs/en/sql-reference/table-functions/cluster/)

[_shard_num documentation](https://clickhouse.tech/docs/en/engines/table-engines/special/distributed/#virtual-columns)

const Settings & settings,
                 const String & config_prefix_,
                 const String & cluster_name)
{
    auto config_prefix = config_prefix_ + "." + cluster_name;
    Poco::Util::AbstractConfiguration::Keys config_keys;
    config.keys(config_prefix, config_keys);
    config_prefix += ".";
    secret = config.getString(config_prefix + "secret", "");
    boost::range::remove_erase(config_keys, "secret");
    if (config_keys.empty())
        throw Exception("No cluster elements (shard, node) specified in config at path " + config_prefix, ErrorCodes::SHARD_HAS_NO_CONNECTIONS);
    UInt32 current_shard_num = 1;
    for (const auto & key : config_keys)
    {
        if (startsWith(key, "node"))
        {
            
            Addresses addresses;
            const auto & prefix = config_prefix + key;
            const auto weight = config.getInt(prefix + ".weight", default_weight);
            addresses.emplace_back(config, prefix, cluster_name, secret, current_shard_num, 1);
            const auto & address = addresses.back();
            ShardInfo info;
            info.shard_num = current_shard_num;
            info.weight = weight;
            if (address.is_local)
                info.local_addresses.push_back(address);
            ConnectionPoolPtr pool = std::make_shared<ConnectionPool>(