**Describe the situation**
multiIf works 10 times slower than If with single condition.

**How to reproduce**
ClickHouse version 21.10

```

SELECT count()
FROM numbers_mt(1000000000)
WHERE NOT ignore(multiIf(number = 0, NULL, toNullable(number)))

┌────count()─┐
│ 1000000000 │
└────────────┘

1 rows in set. Elapsed: 10.267 sec. Processed 1.00 billion rows, 8.00 GB (97.41 million rows/s., 779.25 MB/s.)

SELECT count()
FROM numbers_mt(1000000000)
WHERE NOT ignore(If(number = 0, NULL, toNullable(number)))

┌────count()─┐
│ 1000000000 │
└────────────┘

1 rows in set. Elapsed: 1.010 sec. Processed 1.00 billion rows, 8.00 GB (990.63 million rows/s., 7.93 GB/s.)
```

**Expected performance**
The same performance for multiIf and if.

{
    GroupByKeysInfo data;
    
    for (const auto & group_key : group_by_keys)
    {
        
        if (group_key->as<ASTExpressionList>())
        {
            const auto express_list_ast = group_key->as<const ASTExpressionList &>();
            for (const auto & group_elem : express_list_ast.children)
            {
                data.key_names.insert(group_elem->getColumnName());
            }
        }
        else
        {
            if (group_key->as<ASTFunction>())
                data.has_function = true;
            data.key_names.insert(group_key->getColumnName());
        }
    }
    return data;
}
void optimizeGroupByFunctionKeys(ASTSelectQuery * select_query)