**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]      │
└─────────┴──────────────┘
```

String getName() const override
    {
        return name;
    }
    size_t getNumberOfArguments() const override { return 1; }
    bool isInjective(const ColumnsWithTypeAndName &) const override { return true; }
    DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
    {
        
        if (!isString(arguments[0]))
        {
            const auto * ptr = checkAndGetDataType<DataTypeFixedString>(arguments[0].get());
            if (!ptr || ptr->getN() != uuid_text_length)
                throw Exception("Illegal type " + arguments[0]->getName() +
                                " of argument of function " + getName() +
                                ", expected FixedString(" + toString(uuid_text_length) + ")",
                                ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
        }
        return std::make_shared<DataTypeFixedString>(uuid_bytes_length);
    }
    bool useDefaultImplementationForConstants() const override { return true; }