**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.


{
    return Tuple(collections::map<Tuple>(elems, [] (const DataTypePtr & elem) { return elem->getDefault(); }));
}
void DataTypeTuple::insertDefaultInto(IColumn & column) const
{
    addElementSafe(elems, column, [&]
    {
        for (const auto & i : collections::range(0, elems.size()))
            elems[i]->insertDefaultInto(extractElementColumn(column, i));
    });
}
bool DataTypeTuple::equals(const IDataType & rhs) const
{
    if (typeid(rhs) != typeid(*this))
        return false;
    const DataTypeTuple & rhs_tuple = static_cast<const DataTypeTuple &>(rhs);
    size_t size = elems.size();
    if (size != rhs_tuple.elems.size())
        return false;
    for (size_t i = 0; i < size; ++i)
        if (!elems[i]->equals(*rhs_tuple.elems[i]) || names[i] != rhs_tuple.names[i])
            return false;
    return true;
}
size_t DataTypeTuple::getPositionByName(const String & name) const