**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.

const Columns & key_columns,
        const DataTypes & key_types,
        const ColumnPtr & default_values_column) const override;
    ColumnUInt8::Ptr hasKeys(const Columns & key_columns, const DataTypes & key_types) const override;
    Pipe read(const Names & column_names, size_t max_block_size) const override;
    
    using Coord = Float32;
    
    using Point = bg::model::d2::point_xy<Coord, bg::cs::cartesian>;
    
    using Polygon = bg::model::polygon<Point>;
    
    using Ring = bg::model::ring<Point>;
protected:
    /** Returns true if the given point can be found in the polygon dictionary.
     *  If true id is set to the index of a polygon containing the given point.
     *  Overridden in different implementations of this interface.
     */
    virtual bool find(const Point & point, size_t & polygon_index) const = 0;
    std::vector<Polygon> polygons;
    const DictionaryStructure dict_struct;
    const DictionarySourcePtr source_ptr;
    const DictionaryLifetime dict_lifetime;
    const InputType input_type;
    const PointType point_type;
private:
    /** Helper functions for loading the data from the configuration.
     *  The polygons serving as keys are extracted into boost types.
     *  All other values are stored in one column per attribute.
     */