**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'
```
{
    metadata_snapshot->check(column_names, getVirtuals(), getStorageID());
    const auto access = context->getAccess();
    const bool check_access_for_databases = !access->isGranted(AccessType::SHOW_TABLES);
    
    std::map<String, std::map<String, StoragePtr>> replicated_tables;
    for (const auto & db : DatabaseCatalog::instance().getDatabases())
    {
        
        if (!db.second->canContainMergeTreeTables())
            continue;
        const bool check_access_for_tables = check_access_for_databases && !access->isGranted(AccessType::SHOW_TABLES, db.first);
        for (auto iterator = db.second->getTablesIterator(context); iterator->isValid(); iterator->next())
        {
            const auto & table = iterator->table();
            if (!table)
                continue;
            if (!dynamic_cast<const StorageReplicatedMergeTree *>(table.get()))
                continue;
            if (check_access_for_tables && !access->isGranted(AccessType::SHOW_TABLES, db.first, iterator->name()))
                continue;
            replicated_tables[db.first][iterator->name()] = table;
        }
    }
    
    bool with_zk_fields = false;
    for (const auto & column_name : column_names)
    {
        if (   column_name == "log_max_index"
            || column_name == "log_pointer"