**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.

{
    if (!select.select() || select.select()->children.empty())
        return;
    const ASTSelectQuery * subselect = getSimpleSubselect(select);
    if (!subselect)
        return;
    std::unordered_set<String> distinct_names = getDistinctNames(*subselect);
    std::unordered_set<String> selected_names;
    
    for (const auto & id : select.select()->children)
    {
        const auto * identifier = id->as<ASTIdentifier>();
        if (!identifier)
            return;
        String name = identifier->shortName();
        if (!distinct_names.contains(name))
            return; 
        selected_names.insert(name);
    }
    
    
    if (selected_names.size() != distinct_names.size())
        return;
    select.distinct = false;
}
void optimizeMonotonousFunctionsInOrderBy(ASTSelectQuery * select_query, ContextPtr context,