GHSA-h5x4-m2qf-r4f2: Diesel's SQLite backend has possible UTF-8 corruption

Diesel uses the sqlite3_value_text function to receive strings from SQLite while deserializing query results. We misinterpreted the corresponding SQLite documentation that this function always returns a UTF-8 encoded string values as *const c_char. Based on that we used str::from_utf8_unchecked to construct a Rust string slice without any additional UTF-8 checks in place. It turned out that this function doesn’t always return correct UTF-8 strings. For field of the SQLite side storage type BLOB this pointer can contain arbitrary bytes, which makes the usage of str::from_utf8_unchecked unsound as this violates the safety contract of str to only contain valid UTF-8 encoded Strings.