**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'
```
{
    auto zookeeper = getZooKeeper();
    
    String quorum_status_path = fs::path(zookeeper_path) / "quorum" / "status";
    if (is_parallel)
        quorum_status_path = fs::path(zookeeper_path) / "quorum" / "parallel" / part_name;
    
    const String quorum_last_part_path = fs::path(zookeeper_path) / "quorum" / "last_part";
    String value;
    Coordination::Stat stat;
    
    while (zookeeper->tryGet(quorum_status_path, value, &stat))
    {
        ReplicatedMergeTreeQuorumEntry quorum_entry(value);
        if (quorum_entry.part_name != part_name)
        {
            LOG_TRACE(log, "Quorum {}, already achieved for part {} current part {}",
                      quorum_status_path, part_name, quorum_entry.part_name);
            
            break;
        }
        quorum_entry.replicas.insert(replica_name);
        if (quorum_entry.replicas.size() >= quorum_entry.required_number_of_replicas)
        {
            
            LOG_TRACE(log, "Got {} replicas confirmed quorum {}, going to remove node",
                      quorum_entry.replicas.size(), quorum_status_path);
            Coordination::Requests ops;
            Coordination::Responses responses;