These are subtasks from PERF-3313:

1. ClickBench hits.json – Convert e.g. first ~1M objects to BSON and upload to SE dsi-donot-remove bucket.
2. _writeTestPipeBsonFile() - Create this as another new test shell function that reads from a BSON file and writes the objects it contains to a named pipe. (SERVER-70392 is a reference for this.)
3. jstests/noPassthrough/external_data_source.js - Add a test case for #2 to this test.