bigquery: Support Apache Arrow results format in jobs.query #7030

Support requesting and deserializing Apache Arrow IPC results (QueryResultsFormat::Arrow) from jobs.query in google-cloud-bigquery, laying the foundation for shared Arrow deserialization with the BigQuery Storage Read API.

When jobs.query is configured to return Arrow record batches, query results arrive as a serialized Arrow IPC schema and record batch rather than JSON wkt::Struct rows. Supporting Arrow natively inside Row, RowIterator, and FromSql allows zero-overhead columnar decoding without changing the user-facing Row::get / Row::take / #[derive(FromRow)] APIs.