**How to reproduce**
Clickhouse version 20.11.5.18, 20.8.7.15, 20.3.19
```
SELECT
    groupUniqArray(val) AS uniq,
    toTypeName(uniq),
    groupArray(val) AS arr,
    toTypeName(arr)
FROM
(
    SELECT CAST(number % 2, 'Enum(\'hello\' = 1, \'world\' = 0)') AS val
    FROM numbers(2)
)

Query id: d4657f27-c8bd-4174-9947-c6c48d0222d5

┌─uniq──┬─toTypeName(groupUniqArray(val))─┬─arr───────────────┬─toTypeName(groupArray(val))────────────┐
│ [0,1] │ Array(Int8)                     │ ['world','hello'] │ Array(Enum8('world' = 0, 'hello' = 1)) │
└───────┴─────────────────────────────────┴───────────────────┴────────────────────────────────────────┘
```

: public IAggregateFunctionDataHelper<AggregateFunctionGroupUniqArrayGenericData,
        AggregateFunctionGroupUniqArrayGeneric<is_plain_column, Tlimit_num_elem>>
{
    DataTypePtr & input_data_type;
    static constexpr bool limit_num_elems = Tlimit_num_elem::value;
    UInt64 max_elems;
    using State = AggregateFunctionGroupUniqArrayGenericData;
public:
    AggregateFunctionGroupUniqArrayGeneric(const DataTypePtr & input_data_type_, UInt64 max_elems_ = std::numeric_limits<UInt64>::max())
        : IAggregateFunctionDataHelper<AggregateFunctionGroupUniqArrayGenericData, AggregateFunctionGroupUniqArrayGeneric<is_plain_column, Tlimit_num_elem>>({input_data_type_}, {})
        , input_data_type(this->argument_types[0])
        , max_elems(max_elems_) {}
    String getName() const override { return "groupUniqArray"; }
    DataTypePtr getReturnType() const override
    {
        return std::make_shared<DataTypeArray>(input_data_type);
    }
    bool allocatesMemoryInArena() const override
    {
        return true;
    }
    void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override