**Describe the unexpected behaviour**
ClickHouse returns exception if you would try to read polygon dictionary via SELECT query.

**How to reproduce**
ClickHouse version 21.10


```
CREATE DICTIONARY polygon_dict (
    key Array(Array(Array(Array(Float64)))),
    name String,
    value UInt64
)
PRIMARY KEY key
LAYOUT(POLYGON())
SOURCE(CLICKHOUSE(table 'polygon_dict_src'))
LIFETIME(MIN 300 MAX 360);

CREATE TABLE polygon_dict_src
(
    `key` Array(Array(Array(Array(Float64)))),
    `name` String,
    `value` UInt64
)
ENGINE = Log
	
INSERT INTO polygon_dict_src SELECT [[[[1.1,2.1],[5,3],[6,4],[1,4]]]], 'some', 10;


CREATE DICTIONARY polygon_dict (
    key Array(Array(Array(Array(Float64)))),
    name String,
    value UInt64
)
PRIMARY KEY key
LAYOUT(POLYGON())
SOURCE(CLICKHOUSE(table 'polygon_dict_src'))
LIFETIME(MIN 300 MAX 360);

SELECT dictGet(polygon_dict, 'name', (2., 3.)) AS x

┌─x────┐
│ some │
└──────┘

SELECT *
FROM polygon_dict

0 rows in set. Elapsed: 0.008 sec.

Received exception from server (version 21.10.1):
Code: 1. DB::Exception: Received from localhost:9000. DB::Exception: Reading the dictionary is not allowed. (UNSUPPORTED_METHOD)
```


**Expected behavior**
It's allowed to read POLYGON dictionaries via SELECT query.

{
public:
    PolygonDictionaryIndexCell(
            const StorageID & dict_id_,
            const DictionaryStructure & dict_struct_,
            DictionarySourcePtr source_ptr_,
            DictionaryLifetime dict_lifetime_,
            InputType input_type_,
            PointType point_type_,
            size_t min_intersections_,
            size_t max_depth_);
    std::shared_ptr<const IExternalLoadable> clone() const override;
    static constexpr size_t kMinIntersectionsDefault = 1;
    static constexpr size_t kMaxDepthDefault = 5;
private:
    bool find(const Point & point, size_t & polygon_index) const override;
    GridRoot<FinalCellWithSlabs> index;
    const size_t min_intersections;
    const size_t max_depth;
};
}