[BUG] Data Prepper is writting empty DLQ objects

[dlvenable]

Describe the bug

The Data Prepper opensearch sink can write empty DLQ objects to S3 in certain case.

From what I can tell, this mostly occurs from high-level errors from the _bulk request which do not result in underlying items provided with failures.

To Reproduce
Steps to reproduce the behavior:

Configure an index that you do not have permission to write to.

Run Data Prepper and provide input.

I see the following errors:

2023-11-13T18:09:23,902 [dynamodb-pipeline-sink-worker-2-thread-1] WARN  org.opensearch.dataprepper.plugins.sink.opensearch.BulkRetryStrategy - Bulk Operation Failed. Number of retries 5. Retrying...
2023-11-13T18:09:23,906 [dynamodb-pipeline-sink-worker-2-thread-1] WARN  org.opensearch.dataprepper.plugins.sink.opensearch.BulkRetryStrategy - operation = Index, error = OpenSearch exception [type=authorization_exception, reason=User does not have permissions for the requested resource]
2023-11-13T18:09:23,909 [dynamodb-pipeline-sink-worker-2-thread-1] WARN  org.opensearch.dataprepper.plugins.sink.opensearch.BulkRetryStrategy - operation = Index, error = OpenSearch exception [type=authorization_exception, reason=User does not have permissions for the requested resource]
2023-11-13T18:09:50,577 [dynamodb-pipeline-sink-worker-2-thread-1] WARN  org.opensearch.dataprepper.plugins.sink.opensearch.BulkRetryStrategy - Bulk Operation Failed. Number of retries 10. Retrying...
2023-11-13T18:09:50,579 [dynamodb-pipeline-sink-worker-2-thread-1] WARN  org.opensearch.dataprepper.plugins.sink.opensearch.BulkRetryStrategy - operation = Index, error = OpenSearch exception [type=authorization_exception, reason=User does not have permissions for the requested resource]
2023-11-13T18:09:50,579 [dynamodb-pipeline-sink-worker-2-thread-1] WARN  org.opensearch.dataprepper.plugins.sink.opensearch.BulkRetryStrategy - operation = Index, error = OpenSearch exception [type=authorization_exception, reason=User does not have permissions for the requested resource]

I also got 8 S3 objects in the DLQ. Each looked like:

{"dlqObjects":[]}

Expected behavior

The DLQ should include one item per failed document. It should include the high-level error instead of the individual item error.

Environment (please complete the following information):

Data Prepper main working toward 2.6.0.

Additional context

N/A

[dlvenable]

I am getting this error with an Amazon OpenSearch Serverless collection. In particular, I can see it when the role I use has access to the collection, but not the necessary permissions to create an index.