Ambiguities row/eof packets in the text protocol for very big rows

The following fails:

```
SELECT REPEAT('a', 0x1000000)
```

Because a `string_lenenc` with such size starts with the EOF packet header. This looks like a design issue in the protocol. Other language drivers solve this by first attempting to parse the packet as a row, and then attempting it as an EOF packet on failure.

Start by reproducing the failure with SELECT REPEAT('a', 0x1000000), then inspect the text-protocol parsing path for row and EOF packets. Compare how other language drivers distinguish these packet types. Done means the large-row response is parsed correctly without confusing it with an EOF packet.

Written by the indexing model from the issue text.