**Describe what's wrong**

Query with rollup using same selected field name as the name of underlying column reports structure mismatch

**Does it reproduce on recent release?**

yes

**How to reproduce**

`21.9.2.17`

```sql
CREATE TABLE test
(
    `d` DateTime,
    `a` LowCardinality(String),
    `b` UInt64
)
ENGINE = MergeTree
PARTITION BY toDate(d)
ORDER BY d;

SELECT *
FROM (
    SELECT
        a,
        max((d, b)).2 AS value
    FROM test
    GROUP BY rollup(a)
)
WHERE a <> '';
```

**Expected behavior**

This used to return an ok result on v21.8

**Error message and/or stacktrace**

> Code: 352. DB::Exception: Block structure mismatch in (columns with identical name must have identical structure) stream: different columns:
> notEquals(a, '') LowCardinality(UInt8) ColumnLowCardinality(size = 0, UInt8(size = 0), ColumnUnique(size = 1, UInt8(size = 1)))
> notEquals(a, '') LowCardinality(UInt8) Const(size = 0, ColumnLowCardinality(size = 1, UInt8(size = 1), ColumnUnique(size = 2, UInt8(size = 2)))). (AMBIGUOUS_COLUMN_NAME) (version 21.9.2.17 (official build))



else
    {
        if (prepared_input)
        {
            auto prepared_source_step
                = std::make_unique<ReadFromPreparedSource>(Pipe(std::make_shared<SourceFromInputStream>(prepared_input)), context);
            query_plan.addStep(std::move(prepared_source_step));
        }
        else if (prepared_pipe)
        {
            auto prepared_source_step = std::make_unique<ReadFromPreparedSource>(std::move(*prepared_pipe), context);
            query_plan.addStep(std::move(prepared_source_step));
        }
        if (from_stage == QueryProcessingStage::WithMergeableState &&
            options.to_stage == QueryProcessingStage::WithMergeableState)
            intermediate_stage = true;
        
        
        if (from_stage >= QueryProcessingStage::WithMergeableStateAfterAggregation)
            from_aggregation_stage = true;
        
        if (options.to_stage >= QueryProcessingStage::WithMergeableStateAfterAggregation)
            to_aggregation_stage = true;
        
        executeFetchColumns(from_stage, query_plan);
        LOG_TRACE(log, "{} -> {}", QueryProcessingStage::toString(from_stage), QueryProcessingStage::toString(options.to_stage));
    }
    if (options.to_stage > QueryProcessingStage::FetchColumns)
    {
        auto preliminary_sort = [&]()