[JS] Read and write int64/uint64 as strings in integration test JSON format

**Reporter**: [Wes McKinney](https://issues.apache.org/jira/browse/ARROW-6516) / @wesm
#### Related issues:
- [[Developer] Tracking issue: use strings for 64-bit int64 and uint64 in integration test JSON format](https://github.com/apache/arrow/issues/22880) (is a child of)

_{**Note**: *This issue was originally created as [ARROW-6516](https://issues.apache.org/jira/browse/ARROW-6516). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}