**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'
```
|| column_name == "total_replicas"
            || column_name == "active_replicas"
            || column_name == "zookeeper_exception")
        {
            with_zk_fields = true;
            break;
        }
    }
    MutableColumnPtr col_database_mut = ColumnString::create();
    MutableColumnPtr col_table_mut = ColumnString::create();
    MutableColumnPtr col_engine_mut = ColumnString::create();
    for (auto & db : replicated_tables)
    {
        for (auto & table : db.second)
        {
            col_database_mut->insert(db.first);
            col_table_mut->insert(table.first);
            col_engine_mut->insert(table.second->getName());
        }
    }
    ColumnPtr col_database = std::move(col_database_mut);
    ColumnPtr col_table = std::move(col_table_mut);
    ColumnPtr col_engine = std::move(col_engine_mut);
    
    {
        Block filtered_block
        {
            { col_database, std::make_shared<DataTypeString>(), "database" },
            { col_table, std::make_shared<DataTypeString>(), "table" },
            { col_engine, std::make_shared<DataTypeString>(), "engine" },