**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.


: elems(elems_), names(names_), have_explicit_names(true)
{
    size_t size = elems.size();
    if (names.size() != size)
        throw Exception("Wrong number of names passed to constructor of DataTypeTuple", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
    if (auto exception = checkTupleNames(names))
        throw std::move(*exception);
}
std::string DataTypeTuple::doGetName() const
{
    size_t size = elems.size();
    WriteBufferFromOwnString s;
    s << "Tuple(";
    for (size_t i = 0; i < size; ++i)
    {
        if (i != 0)
            s << ", ";
        if (have_explicit_names)
            s << backQuoteIfNeed(names[i]) << ' ';
        s << elems[i]->getName();
    }
    s << ")";
    return s.str();
}
static inline IColumn & extractElementColumn(IColumn & column, size_t idx)
{
    return assert_cast<ColumnTuple &>(column).getColumn(idx);
}
template <typename F>
static void addElementSafe(const DataTypes & elems, IColumn & column, F && impl)