**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'
```
StorageReplicatedMergeTree::allocateBlockNumber(
    const String & partition_id, const zkutil::ZooKeeperPtr & zookeeper, const String & zookeeper_block_id_path, const String & zookeeper_path_prefix) const
{
    String zookeeper_table_path;
    if (zookeeper_path_prefix.empty())
        zookeeper_table_path = zookeeper_path;
    else
        zookeeper_table_path = zookeeper_path_prefix;
    
    Coordination::Requests deduplication_check_ops;
    if (!zookeeper_block_id_path.empty())
    {
        deduplication_check_ops.emplace_back(zkutil::makeCreateRequest(zookeeper_block_id_path, "", zkutil::CreateMode::Persistent));
        deduplication_check_ops.emplace_back(zkutil::makeRemoveRequest(zookeeper_block_id_path, -1));
    }
    String block_numbers_path = fs::path(zookeeper_table_path) / "block_numbers";
    String partition_path = fs::path(block_numbers_path) / partition_id;
    if (!existsNodeCached(partition_path))
    {
        Coordination::Requests ops;