**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'
```
String replica = findReplicaHavingPart(entry.new_part_name, true);    
        if (!replica.empty())
        {
            LOG_DEBUG(log, "Prefer to fetch {} from replica {}", entry.new_part_name, replica);
            return false;
        }
    }
    MergeTreePartInfo new_part_info = MergeTreePartInfo::fromPartName(
        entry.new_part_name, format_version);
    MutationCommands commands = queue.getMutationCommands(source_part, new_part_info.mutation);
    
    
    ReservationPtr reserved_space = reserveSpace(estimated_space_for_result, source_part->volume);
    auto table_lock = lockForShare(
            RWLockImpl::NO_QUERY, storage_settings_ptr->lock_acquire_timeout_for_background_operations);
    StorageMetadataPtr metadata_snapshot = getInMemoryMetadataPtr();
    MutableDataPartPtr new_part;
    Transaction transaction(*this);
    FutureMergedMutatedPart future_mutated_part;
    future_mutated_part.name = entry.new_part_name;
    future_mutated_part.uuid = entry.new_part_uuid;
    future_mutated_part.parts.push_back(source_part);
    future_mutated_part.part_info = new_part_info;
    future_mutated_part.updatePath(*this, reserved_space);
    future_mutated_part.type = source_part->getType();
    MergeList::EntryPtr merge_entry = getContext()->getMergeList().insert(getStorageID(), future_mutated_part);
    Stopwatch stopwatch;
    auto write_part_log = [&] (const ExecutionStatus & execution_status)