Write jsonb strings needing an escape as TEXTJ

[LucaCappelletti94]

write_jsonb_string reached for TEXTJ only when a string held a control character, so a string containing a quote or a backslash went out as TEXT with the character raw in the payload. a"b became 37 61 22 62, which sqlite reports as invalid through json_valid(blob, 8) and refuses in json(), because TEXT is defined as a payload that renders as JSON unchanged. Diesel reads its own blob back fine, so what breaks is every sqlite JSON function applied to a column diesel wrote.

Any string carrying a byte JSON has to escape, meaning anything below 0x20 plus the quote and the backslash, now goes down the TEXTJ path that already existed for control characters. TEXTRAW would also be well formed, but TEXTJ is byte for byte what sqlite's own jsonb('"a\"b"') writes, so a blob diesel wrote stays comparable with one sqlite wrote for the same value. The scan moved from char::is_control to bytes at the same time, since JSON escapes nothing above 0x1F while is_control also covers U+007F to U+009F, which sqlite stores as plain TEXT.

This came out of a fuzzer I am writing for diesel's deserialization code.