Update S3 ListObjects to ListObjectsV2

Presently we're using an older api: https://docs.aws.amazon.com/sdk-for-go/api/service/s3/#S3.ListObjects to list objects, the new one is here: https://docs.aws.amazon.com/sdk-for-go/api/service/s3/#S3.ListObjectsV2

This API has been revised. We recommend that you use the newer version, ListObjectsV2, when developing applications. For > backward compatibility, Amazon S3 continues to support ListObjects.

As Stan Hu mentioned here #21 (comment 287862885) it's possible we could see an improvement in memory usage with this change.

Using the Go SDK it does not appear that it will take significant effort to update to ListObjectsV2 from ListObjects.