**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 (!children.empty())
    {
        LOG_TRACE(log, "Found zookeper locks for {}", zookeeper_part_uniq_node);
        return false;
    }
    zookeeper->tryRemove(zookeeper_part_uniq_node);
    
    children.clear();
    zookeeper->tryGetChildren(zookeeper_part_node, children);
    if (children.empty())
        
        zookeeper->tryRemove(zookeeper_part_node);
    return true;
}
bool StorageReplicatedMergeTree::tryToFetchIfShared(
    const IMergeTreeDataPart & part,
    const DiskPtr & disk,
    const String & path)
{
    const auto settings = getSettings();
    auto disk_type = disk->getType();
    if (!(disk->supportZeroCopyReplication() && settings->allow_remote_fs_zero_copy_replication))
        return false;
    String replica = getSharedDataReplica(part, disk_type);
    
    if (replica.empty())
        return false;
    return executeFetchShared(replica, part.name, disk, path);
}
String StorageReplicatedMergeTree::getSharedDataReplica(