**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.


extern const int NOT_FOUND_COLUMN_IN_BLOCK;
    extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
    extern const int SIZES_OF_COLUMNS_IN_TUPLE_DOESNT_MATCH;
    extern const int ILLEGAL_INDEX;
    extern const int LOGICAL_ERROR;
}
DataTypeTuple::DataTypeTuple(const DataTypes & elems_)
    : elems(elems_), have_explicit_names(false)
{
    
    size_t size = elems.size();
    names.resize(size);
    for (size_t i = 0; i < size; ++i)
        names[i] = toString(i + 1);
}
static std::optional<Exception> checkTupleNames(const Strings & names)
{
    std::unordered_set<String> names_set;
    for (const auto & name : names)
    {
        if (name.empty())
            return Exception("Names of tuple elements cannot be empty", ErrorCodes::BAD_ARGUMENTS);
        if (isNumericASCII(name[0]))
            return Exception("Explicitly specified names of tuple elements cannot start with digit", ErrorCodes::BAD_ARGUMENTS);
        if (!names_set.insert(name).second)
            return Exception("Names of tuple elements must be unique", ErrorCodes::DUPLICATE_COLUMN);
    }
    return {};
}
DataTypeTuple::DataTypeTuple(const DataTypes & elems_, const Strings & names_)