**Use case**

Currently, `system.replicas` table has `total_replicas` and `active_replicas` columns which are useful to check/alert when some replicas are down. One problem, these columns are numbers. They tell when there is a problem, but you need to further check ZooKeeper or query all the nodes to detect what exact replicas (hosts) are down/inactive/have problems.

**Describe the solution you'd like**

Add a replicas column maybe as a map which would contain the replica name, and it's status. Or, add 2 array columns with `replica_names` and `active_replica_names`

**Alternative**

Something along the line

```sql
select path, value from system.zookeeper where path IN (
    select concat(path, '/', name) from system.zookeeper where path in (select concat(zookeeper_path, '/replicas') from system.replicas)
)
and name = 'is_active'
```
zkutil::CreateMode::Persistent));
        ops.emplace_back(zkutil::makeCreateRequest(replica_path + "/flags", "",
            zkutil::CreateMode::Persistent));
        ops.emplace_back(zkutil::makeCreateRequest(replica_path + "/is_lost", is_lost_value,
            zkutil::CreateMode::Persistent));
        ops.emplace_back(zkutil::makeCreateRequest(replica_path + "/metadata", ReplicatedMergeTreeTableMetadata(*this, metadata_snapshot).toString(),
            zkutil::CreateMode::Persistent));
        ops.emplace_back(zkutil::makeCreateRequest(replica_path + "/columns", metadata_snapshot->getColumns().toString(),
            zkutil::CreateMode::Persistent));
        ops.emplace_back(zkutil::makeCreateRequest(replica_path + "/metadata_version", std::to_string(metadata_version),
            zkutil::CreateMode::Persistent));
        
        ops.emplace_back(zkutil::makeSetRequest(zookeeper_path + "/replicas", "last added replica: " + replica_name, replicas_stat.version));
        Coordination::Responses responses;
        code = zookeeper->tryMulti(ops, responses);
        switch (code)
        {
            case Coordination::Error::ZNODEEXISTS:
                throw Exception(ErrorCodes::REPLICA_IS_ALREADY_EXIST, "Replica {} already exists", replica_path);
            case Coordination::Error::ZBADVERSION:
                LOG_ERROR(log, "Retrying createReplica(), because some other replicas were created at the same time");
                break;
            case Coordination::Error::ZNONODE:
                throw Exception(ErrorCodes::ALL_REPLICAS_LOST, "Table {} was suddenly removed", zookeeper_path);
            default:
                zkutil::KeeperMultiException::check(code, ops, responses);
        }
    } while (code == Coordination::Error::ZBADVERSION);
}
void StorageReplicatedMergeTree::drop()