**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.


{
    size_t size = elems.size();
    for (size_t i = 0; i < size; ++i)
        if (names[i] == name)
            return i;
    throw Exception("Tuple doesn't have element with name '" + name + "'", ErrorCodes::NOT_FOUND_COLUMN_IN_BLOCK);
}
String DataTypeTuple::getNameByPosition(size_t i) const
{
    if (i == 0 || i > names.size())
        throw Exception(ErrorCodes::ILLEGAL_INDEX, "Index of tuple element ({}) if out range ([1, {}])", i, names.size());
    return names[i - 1];
}
bool DataTypeTuple::textCanContainOnlyValidUTF8() const
{
    return std::all_of(elems.begin(), elems.end(), [](auto && elem) { return elem->textCanContainOnlyValidUTF8(); });
}
bool DataTypeTuple::haveMaximumSizeOfValue() const
{
    return std::all_of(elems.begin(), elems.end(), [](auto && elem) { return elem->haveMaximumSizeOfValue(); });
}
bool DataTypeTuple::isComparable() const