**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'
```
else 
            {
                new_metadata.table_ttl = TTLTableDescription{};
            }
        }
    }
    
    new_metadata.column_ttls_by_name.clear();
    for (const auto & [name, ast] : new_metadata.columns.getColumnTTLs())
    {
        auto new_ttl_entry = TTLDescription::getTTLFromAST(ast, new_metadata.columns, getContext(), new_metadata.primary_key);
        new_metadata.column_ttls_by_name[name] = new_ttl_entry;
    }
    if (new_metadata.partition_key.definition_ast != nullptr)
        new_metadata.partition_key.recalculateWithNewColumns(new_metadata.columns, getContext());
    if (!metadata_diff.sorting_key_changed) 
        new_metadata.sorting_key.recalculateWithNewColumns(new_metadata.columns, getContext());
    
    if (new_metadata.primary_key.definition_ast != nullptr)
    {
        new_metadata.primary_key.recalculateWithNewColumns(new_metadata.columns, getContext());
    }
    else
    {
        new_metadata.primary_key = KeyDescription::getKeyFromAST(new_metadata.sorting_key.definition_ast, new_metadata.columns, getContext());
        new_metadata.primary_key.definition_ast = nullptr;
    }
    if (!metadata_diff.sampling_expression_changed && new_metadata.sampling_key.definition_ast != nullptr)
        new_metadata.sampling_key.recalculateWithNewColumns(new_metadata.columns, getContext());
    if (!metadata_diff.skip_indices_changed)