For [the rule in the list](https://github.com/ClickHouse/ClickHouse/blob/82fc7375dd3ac4faae6c3b0db9f3a28fb2802d05/tests/config/top_level_domains/public_suffix_list.dat#L6430) `*.sch.uk` 

and domain like `www.something.sheffield.sch.uk`  the correct / expected result is `sheffield.sch.uk`

Example with python (correct)

```
-- pip install publicsuffix2
-- python3
>>> from publicsuffix2 import get_public_suffix
>>> get_public_suffix('www.something.sheffield.sch.uk')
'something.sheffield.sch.uk'
```

Same from clickhouse:
```
SELECT cutToFirstSignificantSubdomain('www.something.sheffield.sch.uk')

Query id: 9661461f-a393-43ea-97a1-47c0a8850515

┌─cutToFirstSignificantSubdomain('www.something.sheffield.sch.uk')─┐
│ sch.uk                                                           │
└──────────────────────────────────────────────────────────────────┘
```

/cc @azat 
}
        if (!last_3_periods[0])
            return;
        if (!last_3_periods[1])
        {
            res_size = last_3_periods[0] - begin;
            return;
        }
        if (!last_3_periods[2])
            last_3_periods[2] = begin - 1;
        const auto * end_of_level_domain = find_first_symbols<'/'>(last_3_periods[0], end);
        if (!end_of_level_domain)
        {
            end_of_level_domain = end;
        }
        if (lookup(last_3_periods[1] + 1, end_of_level_domain - last_3_periods[1] - 1))
        {
            res_data += last_3_periods[2] + 1 - begin;
            res_size = last_3_periods[1] - last_3_periods[2] - 1;
        }
        else
        {
            res_data += last_3_periods[1] + 1 - begin;
            res_size = last_3_periods[0] - last_3_periods[1] - 1;
        }
    }
    
    
    template <class Lookup>
    static void executeCustom(const Lookup & lookup, const Pos data, const size_t size, Pos & res_data, size_t & res_size, Pos * out_domain_end = nullptr)