Fix DeleteObjects to throw DeleteObjectsException instead of AmazonS3Exception

[AlexDaines]

Description

Added UnmarshallException method override to DeleteObjectsResponseUnmarshaller to ensure that all DeleteObjects operation failures consistently throw DeleteObjectsException instead of the generic AmazonS3Exception.
The fix creates a DeleteObjectsResponse containing structured error information and wraps it in a DeleteObjectsException, preserving all error details (ErrorCode, RequestId, StatusCode) while providing the expected exception type.

Motivation and Context

Fixes issue #3828 reported inconsistent exception handling for DeleteObjects operations.

Testing

• Tested with invalid keys (too long), confirming DeleteObjectsException is now thrown
• Verified that exception contains proper error information in Response.DeleteErrors collection
• Validated that ErrorCode, RequestId, and StatusCode are properly preserved

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project
• My change requires a change to the documentation
• I have updated the documentation accordingly
• I have read the README document
• I have added tests to cover my changes
• All new and existing tests passed

License

• I confirm that this pull request can be released under the Apache 2 license

[grsw92]

@AlexDaines does this solution guarantee that object under valid key gets deleted when sent along with invalid key in a single DeleteObjectsRequest?