**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'
```
LOG_DEBUG(log, "Can't use {} as source table for REPLACE PARTITION command. It does not exist.", source_table_id.getNameForLogs());
            return 0;
        }
        auto src_metadata_snapshot = source_table->getInMemoryMetadataPtr();
        MergeTreeData * src_data = nullptr;
        try
        {
            src_data = &checkStructureAndGetMergeTreeData(source_table, src_metadata_snapshot, dst_metadata_snapshot);
        }
        catch (Exception &)
        {
            LOG_INFO(log, "Can't use {} as source table for REPLACE PARTITION command. Will fetch all parts. Reason: {}", source_table_id.getNameForLogs(), getCurrentExceptionMessage(false));
            return 0;
        }
        table_lock_holder_src_table = source_table->lockForShare(
                RWLockImpl::NO_QUERY, getSettings()->lock_acquire_timeout_for_background_operations);
        DataPartStates valid_states{
            MergeTreeDataPartState::PreCommitted, MergeTreeDataPartState::Committed, MergeTreeDataPartState::Outdated};
        size_t num_clonable_parts = 0;
        for (PartDescriptionPtr & part_desc : parts_to_add)
        {
            auto src_part = src_data->getPartIfExists(part_desc->src_part_info, valid_states);
            if (!src_part)
            {
                LOG_DEBUG(log, "There is no part {} in {}", part_desc->src_part_name, source_table_id.getNameForLogs());
                continue;
            }
            String checksum_hex  = src_part->checksums.getTotalChecksumHex();
            if (checksum_hex != part_desc->checksum_hex)
            {