**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'
```
#include <Columns/ColumnString.h>
#include <DataTypes/DataTypeString.h>
#include <DataTypes/DataTypesNumber.h>
#include <DataTypes/DataTypeDateTime.h>
#include <Storages/System/StorageSystemReplicas.h>
#include <Storages/StorageReplicatedMergeTree.h>
#include <Storages/VirtualColumnUtils.h>
#include <Access/ContextAccess.h>
#include <Common/typeid_cast.h>
#include <Databases/IDatabase.h>
#include <Processors/Sources/SourceFromSingleChunk.h>
namespace DB
{
StorageSystemReplicas::StorageSystemReplicas(const StorageID & table_id_)
    : IStorage(table_id_)
{
    StorageInMemoryMetadata storage_metadata;
    storage_metadata.setColumns(ColumnsDescription({
        { "database",                             std::make_shared<DataTypeString>()   },
        { "table",                                std::make_shared<DataTypeString>()   },
        { "engine",                               std::make_shared<DataTypeString>()   },
        { "is_leader",                            std::make_shared<DataTypeUInt8>()    },
        { "can_become_leader",                    std::make_shared<DataTypeUInt8>()    },
        { "is_readonly",                          std::make_shared<DataTypeUInt8>()    },
        { "is_session_expired",                   std::make_shared<DataTypeUInt8>()    },
        { "future_parts",                         std::make_shared<DataTypeUInt32>()   },
        { "parts_to_check",                       std::make_shared<DataTypeUInt32>()   },
        { "zookeeper_path",                       std::make_shared<DataTypeString>()   },
        { "replica_name",                         std::make_shared<DataTypeString>()   },
        { "replica_path",                         std::make_shared<DataTypeString>()   },