**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 auto storage_settings_ptr = getSettings();
    return storage_settings_ptr->index_granularity_bytes != 0 &&
        (storage_settings_ptr->enable_mixed_granularity_parts ||
            (!has_non_adaptive_index_granularity_parts && !other_replicas_fixed_granularity));
}
MutationCommands StorageReplicatedMergeTree::getFirstAlterMutationCommandsForPart(const DataPartPtr & part) const
{
    return queue.getFirstAlterMutationCommandsForPart(part);
}
void StorageReplicatedMergeTree::startBackgroundMovesIfNeeded()
{
    if (areBackgroundMovesNeeded())
        background_moves_executor.start();
}
std::unique_ptr<MergeTreeSettings> StorageReplicatedMergeTree::getDefaultSettings() const