**Use case**

Convert bitmask to position.
It would allow us to directly use FLAT dictionary or Enum datatype without jumping around slow `bitmasktoArray` and `arrayMap`

**Describe the solution you'd like**

```
SELECT
    arrayMap(x -> log2(x), bitmaskToArray(100)) AS bitmask,
    bitPositions(100)  AS bitpositions

┌─bitmask─┬─bitpositions─┐
│ [2,5,6] │ [2,5,6]      │
└─────────┴──────────────┘
```

ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t ) const override
    {
        const ColumnWithTypeAndName & col_type_name = arguments[0];
        const ColumnPtr & column = col_type_name.column;
        if (const auto * col_in = checkAndGetColumn<ColumnString>(column.get()))
        {
            const auto & vec_in = col_in->getChars();
            const auto & offsets_in = col_in->getOffsets();
            const size_t size = offsets_in.size();
            auto col_res = ColumnFixedString::create(uuid_bytes_length);
            ColumnString::Chars & vec_res = col_res->getChars();
            vec_res.resize(size * uuid_bytes_length);
            size_t src_offset = 0;
            size_t dst_offset = 0;
            for (size_t i = 0; i < size; ++i)
            {
                
                
                size_t string_size = offsets_in[i] - src_offset;
                if (string_size == uuid_text_length + 1)
                    parseUUID(&vec_in[src_offset], &vec_res[dst_offset]);
                else
                    memset(&vec_res[dst_offset], 0, uuid_bytes_length);
                dst_offset += uuid_bytes_length;
                src_offset += string_size;
            }
            return col_res;