**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 lock = lockForAlter(RWLockImpl::NO_QUERY, getSettings()->lock_acquire_timeout_for_background_operations);
        LOG_INFO(log, "Metadata changed in ZooKeeper. Applying changes locally.");
        auto metadata_diff = ReplicatedMergeTreeTableMetadata(*this, getInMemoryMetadataPtr()).checkAndFindDiff(metadata_from_entry);
        setTableStructure(std::move(columns_from_entry), metadata_diff);
        metadata_version = entry.alter_version;
        LOG_INFO(log, "Applied changes to the metadata of the table. Current metadata version: {}", metadata_version);
    }
    
    zookeeper->createOrUpdate(fs::path(replica_path) / "metadata_version", std::to_string(metadata_version), zkutil::CreateMode::Persistent);
    return true;
}
std::set<String> StorageReplicatedMergeTree::getPartitionIdsAffectedByCommands(
    const MutationCommands & commands, ContextPtr query_context) const
{
    std::set<String> affected_partition_ids;
    for (const auto & command : commands)
    {
        if (!command.partition)
        {
            affected_partition_ids.clear();
            break;
        }
        affected_partition_ids.insert(
            getPartitionIDFromQuery(command.partition, query_context)
        );
    }
    return affected_partition_ids;
}
PartitionBlockNumbersHolder StorageReplicatedMergeTree::allocateBlockNumbersInAffectedPartitions(