HDDS-16362. GetObjectAttributes ObjectParts should return Part entries for FSO buckets

[Gargi-jais11]

What changes were proposed in this pull request?

Extend GetObjectAttributes ObjectParts handling so FSO layout buckets (Ozone’s equivalent of AWS directory buckets) return per-part elements (PartNumber, Size) even when no additional checksum was stored at upload time.

This follows AWS S3 behavior documented in https://docs.aws.amazon.com/AmazonS3/latest/API/API_GetObjectAttributesParts.html:

General-purpose buckets: Part elements are omitted unless an additional checksum (x-amz-checksum-crc32, crc32c, sha1, sha256) was applied.
Directory buckets: Part elements are returned regardless of checksum.

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-16362

How was this patch tested?

Added IT and UT.

// FSO bucket getObjectAttributes returns parts info irrespective of checksum present or not

bash-5.1$ aws s3api get-object-attributes --endpoint-url "$ENDPOINT" \
  --bucket "$BUCKET" --key "$KEY" \
  --object-attributes ObjectParts ObjectSize \
  --output json | jq '.ObjectParts | {TotalPartsCount, IsTruncated, PartCount: (.Parts | length), Parts}'
{
  "TotalPartsCount": 2,
  "IsTruncated": false,
  "PartCount": 2,
  "Parts": [
    {
      "PartNumber": 1,
      "Size": 5242880
    },
    {
      "PartNumber": 2,
      "Size": 8
    }
  ]
}
bash-5.1$ aws s3api get-object-attributes --endpoint-url "$ENDPOINT" \
  --bucket "$BUCKET" --key "$KEY" \
  --object-attributes ObjectParts --max-parts 1 --part-number-marker 0 \
  --output json | jq '.ObjectParts | {IsTruncated, Parts}'
{
  "IsTruncated": true,
  "Parts": [
    {
      "PartNumber": 1,
      "Size": 5242880
    }
  ]
}

// OBS bucket doesnot return part info if checksum not present
bash-5.1$ aws s3api get-object-attributes --endpoint-url "$ENDPOINT" \
  --bucket "$BUCKET" --key "$KEY" \
  --object-attributes ObjectParts ObjectSize \
  --output json | jq '.ObjectParts | {TotalPartsCount, IsTruncated, PartCount: (.Parts | length), Parts}'
{
  "TotalPartsCount": 2,
  "IsTruncated": false,
  "PartCount": 0,
  "Parts": null
}