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

{
public:
    static constexpr auto name = "isIPv4String";
    static FunctionPtr create(ContextPtr) { return std::make_shared<FunctionIsIPv4String>(); }
    String getName() const override { return name; }
    DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
    {
        if (!isString(arguments[0]))
            throw Exception("Illegal type " + arguments[0]->getName() + " of argument of function " + getName(),
                            ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
        return std::make_shared<DataTypeUInt8>();
    }
    ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t ) const override