Make scamper1 mda output to single JSON object (autoloadable)

[stephen-soltesz]

The scamper1 traceroute format by default is four JSON objects, creating a JSONL file per trace. This format is not supported by the autoloading system. Ideally, traceroute-caller would support a native JSON output format for scamper1 traces.

The native scamper structure uses a double array, [][]ScamperLink which the bigquery.InferSchema cannot work with. The etl parser transforms the raw object into a new object that is structured compatibly with BigQuery schemas.

To achive an autoloadable, JSON output for scamper mda traces, this transformation process must be local to the traceroute caller. This does not necessarily imply we must remain backward compatible with scamper1 schema, only that the transform is local and the output is autoloadable JSON.