
**Bug description**
Unlike `cluster()`, `clusterAllReplicas()` does not implement `_shard_num`. 

I would expect
```
SELECT _shard_num
FROM clusterAllReplicas(prod, system.one)
ORDER BY _shard_num ASC
FORMAT PrettyCompactMonoBlock

┌─_shard_num─┐
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
│          0 │
└────────────┘
```
to have an output more useful like
```
SELECT _shard_num
FROM cluster(prod, system.one)
ORDER BY _shard_num ASC
FORMAT PrettyCompactMonoBlock

┌─_shard_num─┐
│          1 │
│          2 │
│          3 │
│          4 │
│          5 │
│          6 │
│          7 │
│          8 │
│          9 │
│         10 │
│         11 │
│         12 │
│         13 │
│         14 │
│         15 │
└────────────┘
```

**Releases where this has been tested**

* v20.3.12.112-stable

**References**

[cluster, clusterAllReplicas documentation](https://clickhouse.tech/docs/en/sql-reference/table-functions/cluster/)

[_shard_num documentation](https://clickhouse.tech/docs/en/engines/table-engines/special/distributed/#virtual-columns)

{
    if (!can_execute)
        throw Exception("Cannot execute mutations interpreter because can_execute flag set to false", ErrorCodes::LOGICAL_ERROR);
    if (!select_interpreter)
        select_interpreter = std::make_unique<InterpreterSelectQuery>(mutation_ast, context, storage, metadata_snapshot, select_limits);
    QueryPlan plan;
    select_interpreter->buildQueryPlan(plan);
    auto pipeline = addStreamsForLaterStages(stages, plan);
    BlockInputStreamPtr result_stream = std::make_shared<PipelineExecutingBlockInputStream>(std::move(*pipeline));
    
    
    if (auto sort_desc = getStorageSortDescriptionIfPossible(result_stream->getHeader()))
        result_stream = std::make_shared<CheckSortedBlockInputStream>(result_stream, *sort_desc);
    if (!updated_header)
        updated_header = std::make_unique<Block>(result_stream->getHeader());
    return result_stream;
}
const Block & MutationsInterpreter::getUpdatedHeader() const