**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'
```
const DataPartPtr & part)
{
    auto zookeeper = getZooKeeper();
    while (true)
    {
        Coordination::Requests ops;
        NameSet absent_part_paths_on_replicas;
        
        checkPartChecksumsAndAddCommitOps(zookeeper, part, ops, part->name, &absent_part_paths_on_replicas);
        
        if (transaction.isEmpty())
            return {};
        
        if (!absent_part_paths_on_replicas.empty())
        {
            Coordination::Requests new_ops;
            for (const String & part_path : absent_part_paths_on_replicas)
            {
                new_ops.emplace_back(zkutil::makeCreateRequest(part_path, "", zkutil::CreateMode::Persistent));
                new_ops.emplace_back(zkutil::makeRemoveRequest(part_path, -1));
            }
            
            new_ops.insert(new_ops.end(), ops.begin(), ops.end());