**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 AlterCommands & commands, ContextPtr query_context, TableLockHolder & table_lock_holder)
{
    assertNotReadonly();
    auto table_id = getStorageID();
    if (commands.isSettingsAlter())
    {
        
        
        StorageInMemoryMetadata future_metadata = getInMemoryMetadata();
        commands.apply(future_metadata, query_context);
        merge_strategy_picker.refreshState();
        changeSettings(future_metadata.settings_changes, table_lock_holder);
        DatabaseCatalog::instance().getDatabase(table_id.database_name)->alterTable(query_context, table_id, future_metadata);
        return;
    }
    auto ast_to_str = [](ASTPtr query) -> String
    {
        if (!query)
            return "";
        return queryToString(query);
    };
    const auto zookeeper = getZooKeeper();
    std::optional<ReplicatedMergeTreeLogEntryData> alter_entry;
    std::optional<String> mutation_znode;
    while (true)
    {
        
        alter_entry.emplace();
        mutation_znode.reset();