[Feature]: Add disable_batch_delete option to support Alibaba Cloud OSS in S3 backend

[yuan7he]

Problem Statement

When using Alibaba Cloud OSS as the AGFS S3 backend, add_resource always fails with a 400 error during temporary directory cleanup after file processing:

failed to delete source directory: failed to delete objects:
operation error S3: DeleteObjects, StatusCode: 400,
api error MissingArgument: Missing Some Required Arguments.

The missing argument is Content-MD5. OSS requires this header for the DeleteObjects (POST /?delete) API, but AWS SDK v2 does not send it by default. This
makes the S3 backend completely unusable with Alibaba Cloud OSS.

Proposed Solution

Add a disable_batch_delete boolean option to S3Config. When set to true, the backend uses sequential single-object DeleteObject calls instead of batch
DeleteObjects. Single-object delete does not require Content-MD5, making it compatible with OSS.

The option defaults to false, so existing users are not affected.

Example configuration:

"s3": {
  "endpoint": "http://s3.oss-cn-beijing.aliyuncs.com",
  "bucket": "your-bucket",
  "region": "cn-beijing",
  "disable_batch_delete": true
}

Use Case

Using Alibaba Cloud OSS (s3.oss-{region}.aliyuncs.com) as the AGFS S3 storage backend. OSS is a widely used object storage service that follows the
S3-compatible API with minor differences — one being the mandatory Content-MD5 header for batch delete operations.