**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'
```
const String & source_replica_path, bool to_detached, size_t quorum, zkutil::ZooKeeper::Ptr zookeeper_)
{
    auto zookeeper = zookeeper_ ? zookeeper_ : getZooKeeper();
    const auto part_info = MergeTreePartInfo::fromPartName(part_name, format_version);
    if (!to_detached)
    {
        if (auto part = getPartIfExists(part_info, {IMergeTreeDataPart::State::Outdated, IMergeTreeDataPart::State::Deleting}))
        {
            LOG_DEBUG(log, "Part {} should be deleted after previous attempt before fetch", part->name);
            
            cleanup_thread.wakeup();
            return false;
        }
    }
    {
        std::lock_guard lock(currently_fetching_parts_mutex);
        if (!currently_fetching_parts.insert(part_name).second)
        {
            LOG_DEBUG(log, "Part {} is already fetching right now", part_name);
            return false;
        }
    }
    SCOPE_EXIT_MEMORY
    ({
        std::lock_guard lock(currently_fetching_parts_mutex);
        currently_fetching_parts.erase(part_name);
    });
    LOG_DEBUG(log, "Fetching part {} from {}", part_name, source_replica_path);
    TableLockHolder table_lock_holder;
    if (!to_detached)