
**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 (stages.size() == 1) 
                stages.emplace_back(context);
            NameSet affected_materialized;
            for (const auto & kv : command.column_to_update_expression)
            {
                const String & column = kv.first;
                auto materialized_it = column_to_affected_materialized.find(column);
                if (materialized_it != column_to_affected_materialized.end())
                {
                    for (const String & mat_column : materialized_it->second)
                        affected_materialized.emplace(mat_column);
                }
                
                
                
                
                
                
                
                
                
                auto type_literal = std::make_shared<ASTLiteral>(columns_desc.getPhysical(column).type->getName());
                const auto & update_expr = kv.second;
                auto updated_column = makeASTFunction("CAST",
                    makeASTFunction("if",
                        getPartitionAndPredicateExpressionForMutationCommand(command),
                        makeASTFunction("CAST",
                            update_expr->clone(),
                            type_literal),
                        std::make_shared<ASTIdentifier>(column)),