**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_query->limitBy())
        return;
    std::set<String> elems_set;
    ASTs & elems = select_query->limitBy()->children;
    ASTs unique_elems;
    unique_elems.reserve(elems.size());
    for (const auto & elem : elems)
    {
        if (elems_set.emplace(elem->getColumnName()).second)
            unique_elems.emplace_back(elem);
    }
    if (unique_elems.size() < elems.size())
        elems = std::move(unique_elems);
}
void optimizeWithConstraints(ASTSelectQuery * select_query,
                             Aliases & ,
                             const NameSet & ,
                             const std::vector<TableWithColumnNamesAndTypes> & ,
                             const StorageMetadataPtr & metadata_snapshot,
                             const bool optimize_append_index)
{
    WhereConstraintsOptimizer(select_query, metadata_snapshot, optimize_append_index).perform();
}
void optimizeSubstituteColumn(ASTSelectQuery * select_query,