**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'
```
{
            if (results[0]->error != Coordination::Error::ZOK)
                throw Exception("Metadata on replica is not up to date with common metadata in Zookeeper. Cannot alter",
                    ErrorCodes::CANNOT_ASSIGN_ALTER);
            
            if (query_context->getZooKeeperMetadataTransaction())
                throw Exception("Cannot execute alter, because mutations version was suddenly changed due to concurrent alter",
                                ErrorCodes::CANNOT_ASSIGN_ALTER);
            continue;
        }
        else
        {
            throw Coordination::Exception("Alter cannot be assigned because of Zookeeper error", rc);
        }
    }
    table_lock_holder.reset();
    std::vector<String> unwaited;
    if (query_context->getSettingsRef().replication_alter_partitions_sync == 2)
    {
        LOG_DEBUG(log, "Updated shared metadata nodes in ZooKeeper. Waiting for replicas to apply changes.");
        unwaited = waitForAllReplicasToProcessLogEntry(*alter_entry, false);
    }
    else if (query_context->getSettingsRef().replication_alter_partitions_sync == 1)
    {
        LOG_DEBUG(log, "Updated shared metadata nodes in ZooKeeper. Waiting for replicas to apply changes.");
        waitForReplicaToProcessLogEntry(replica_name, *alter_entry);
    }
    if (!unwaited.empty())
        throw Exception("Some replicas doesn't finish metadata alter", ErrorCodes::UNFINISHED);
    if (mutation_znode)