**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'
```
Coordination::Requests ops;
    Coordination::Responses responses;
    String drop_lock_path = zookeeper_path + "/dropped/lock";
    ops.emplace_back(zkutil::makeRemoveRequest(zookeeper_path + "/replicas", -1));
    ops.emplace_back(zkutil::makeCreateRequest(zookeeper_path + "/dropped", "", zkutil::CreateMode::Persistent));
    ops.emplace_back(zkutil::makeCreateRequest(drop_lock_path, "", zkutil::CreateMode::Ephemeral));
    Coordination::Error code = zookeeper->tryMulti(ops, responses);
    if (code == Coordination::Error::ZNONODE || code == Coordination::Error::ZNODEEXISTS)
    {
        LOG_WARNING(logger, "Table {} is already started to be removing by another replica right now", remote_replica_path);
    }
    else if (code == Coordination::Error::ZNOTEMPTY)
    {
        LOG_WARNING(logger, "Another replica was suddenly created, will keep the table {}", remote_replica_path);
    }
    else if (code != Coordination::Error::ZOK)
    {
        zkutil::KeeperMultiException::check(code, ops, responses);
    }
    else
    {
        auto metadata_drop_lock = zkutil::EphemeralNodeHolder::existing(drop_lock_path, *zookeeper);
        LOG_INFO(logger, "Removing table {} (this might take several minutes)", zookeeper_path);
        removeTableNodesFromZooKeeper(zookeeper, zookeeper_path, metadata_drop_lock, logger);
    }
}
bool StorageReplicatedMergeTree::removeTableNodesFromZooKeeper(zkutil::ZooKeeperPtr zookeeper,