**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 ColumnPtr & column = arguments[0].column;
        if (const ColumnUInt64 * col = typeid_cast<const ColumnUInt64 *>(column.get()))
        {
            const ColumnUInt64::Container & vec_in = col->getData();
            auto col_res = ColumnString::create();
            ColumnString::Chars & vec_res = col_res->getChars();
            ColumnString::Offsets & offsets_res = col_res->getOffsets();
            vec_res.resize(vec_in.size() * 18); 
            offsets_res.resize(vec_in.size());
            size_t current_offset = 0;
            for (size_t i = 0; i < vec_in.size(); ++i)
            {
                formatMAC(vec_in[i], &vec_res[current_offset]);
                current_offset += 18;
                offsets_res[i] = current_offset;
            }
            return col_res;
        }
        else
            throw Exception("Illegal column " + arguments[0].column->getName()
            + " of argument of function " + getName(),
            ErrorCodes::ILLEGAL_COLUMN);
    }
};
struct ParseMACImpl
{
    static constexpr size_t min_string_size = 17;
    static constexpr size_t max_string_size = 17;