Expose bulk operations in Bulk Result

Right now there's no way to access the operations/batches after a bulk op is executed. See: https://docs.mongodb.com/manual/reference/method/Bulk.getOperations/

Right now we're looking directly in `BulkOp.s.batches`/currentBatch/currentUpdateBatch/currentInsertBatch/currentRemoveBatch to find the list of operations/batches. Is there a better way?