**Describe what's wrong**

It's not possible to use digit as tuple name, so it's not possible to parse JSON files to nested tuple structure with JSONExtract.

**Does it reproduce on recent release?**

Yes

ClickHouse 21.12


**How to reproduce**
```
WITH
    '{"1":{"key":"value"}}' AS data,
    JSONExtract(data, 'Tuple("1" Tuple(key String))') AS parsed_json
SELECT parsed_json AS ssid

Query id: 5bc7b6cf-155a-421c-ac20-f3be09bd9692


0 rows in set. Elapsed: 0.003 sec.

Received exception from server (version 21.12.1):
Code: 36. DB::Exception: Received from localhost:9000. DB::Exception: Explicitly specified names of tuple elements cannot start with digit: While processing JSONExtract('{"1":{"key":"value"}}' AS data, 'Tuple("1" Tuple(key String))') AS ssid. (BAD_ARGUMENTS)
```

**Expected behavior**

It's possible to parse JSON with digit keys.


#include <base/map.h>
#include <base/range.h>
#include <Common/StringUtils/StringUtils.h>
#include <Columns/ColumnTuple.h>
#include <Core/Field.h>
#include <DataTypes/DataTypeTuple.h>
#include <DataTypes/DataTypeArray.h>
#include <DataTypes/DataTypeFactory.h>
#include <DataTypes/Serializations/SerializationInfo.h>
#include <DataTypes/Serializations/SerializationTuple.h>
#include <DataTypes/Serializations/SerializationNamed.h>
#include <DataTypes/Serializations/SerializationInfoTuple.h>
#include <DataTypes/NestedUtils.h>
#include <Parsers/IAST.h>
#include <Parsers/ASTNameTypePair.h>
#include <Common/assert_cast.h>
#include <Common/quoteString.h>
#include <IO/WriteHelpers.h>
#include <IO/WriteBufferFromString.h>
#include <IO/Operators.h>
namespace DB
{
namespace ErrorCodes
{
    extern const int BAD_ARGUMENTS;
    extern const int DUPLICATE_COLUMN;
    extern const int EMPTY_DATA_PASSED;