`readDumpFile` https://github.com/10gen/mongo/blob/512143ec356794a9df4a5ab67aef05fd1a7a2fce/src/mongo/shell/shell_utils_extended.cpp#L592 can only read a file whose content fits into a single BSONObj (which holds a BSONArray of results).  For larger corpuses, we need a way to pull out multiple BSONObj from a larger dump file to write js tests.

As all return results from shell functions are BSONObj, this probably means we need some sort of iterator-like pattern.