**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.

IColumn::Offsets ring_offsets;
    IColumn::Offsets polygon_offsets;
    IColumn::Offsets multi_polygon_offsets;
    IColumn::Offset points_added = 0;
    IColumn::Offset current_ring = 0;
    IColumn::Offset current_polygon = 0;
    IColumn::Offset current_multi_polygon = 0;
    Offset& operator++()
    {
        ++points_added;
        if (points_added <= ring_offsets[current_ring])
            return *this;
        ++current_ring;
        if (current_ring < polygon_offsets[current_polygon])
            return *this;
        ++current_polygon;
        if (current_polygon < multi_polygon_offsets[current_multi_polygon])
            return *this;
        ++current_multi_polygon;
        return *this;
    }
    bool atLastPolygonOfMultiPolygon() { return current_polygon + 1 == multi_polygon_offsets[current_multi_polygon]; }