**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 old_size = column.size();
    try
    {
        impl();
        
        size_t new_size = column.size();
        for (auto i : collections::range(0, elems.size()))
        {
            const auto & element_column = extractElementColumn(column, i);
            if (element_column.size() != new_size)
            {
                
                
                throw Exception(ErrorCodes::SIZES_OF_COLUMNS_IN_TUPLE_DOESNT_MATCH,
                    "Cannot read a tuple because not all elements are present");
            }
        }
    }
    catch (...)
    {
        for (const auto & i : collections::range(0, elems.size()))
        {
            auto & element_column = extractElementColumn(column, i);
            if (element_column.size() > old_size)
                element_column.popBack(1);
        }
        throw;