### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

Initiating a multipart S3 upload to LocalStack returns an XML document with a root element CreateMultipartUploadOutput. This causes an error in the ex_aws_s3 library I'm using. We've used the combination of LocalStack + ex_aws_s3 successfully for a few years and the error started occurring a few days ago.

### Expected Behavior

The element should be called InitiateMultipartUploadResult.

### How are you starting LocalStack?

With a `docker run` command

### Steps To Reproduce

#### How are you starting localstack (e.g., `bin/localstack` command, arguments, or `docker-compose.yml`)

    docker run -p 4566:4566 localstack/localstack

#### Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)

    aws --debug --endpoint-url=http://localhost:4566 s3api create-multipart-upload --bucket my-bucket --key 'multipart/01'


### Environment

```markdown
- OS: Ubuntu 20.04.5 LTS
- LocalStack: latest
```


### Anything else?

S3 docs specifying InitiateMultipartUploadResult:
https://docs.aws.amazon.com/AmazonS3/latest/API/API_CreateMultipartUpload.html

Reference in official AWS Java client:
https://github.com/aws/aws-sdk-java/blob/ef22b94750d4c155d74b09012b3be5d9d98bbd33/aws-java-sdk-s3/src/main/java/com/amazonaws/services/s3/model/transform/XmlResponsesSaxParser.java#L1865

Where our particular error gets raised in ex_aws_s3:
https://github.com/ex-aws/ex_aws_s3/blob/7e12f2b0578b2620c047d2e44c40a6de8773584a/lib/ex_aws/s3/parsers.ex#L78
if "StorageClass" in object_attrs:
            response["StorageClass"] = key.storage_class
        if "ObjectSize" in object_attrs:
            response["ObjectSize"] = key.size
        if "Checksum" in object_attrs and (checksum_algorithm := key.checksum_algorithm):
            
            
            checksum = get_object_checksum_for_algorithm(
                checksum_algorithm=checksum_algorithm,
                data=key.value,
            )
            response["Checksum"] = {f"Checksum{checksum_algorithm.upper()}": checksum}  
        response["LastModified"] = key.last_modified
        if bucket_name in self.get_store().bucket_versioning_status:
            response["VersionId"] = key.version_id
        if key.multipart:
            response["ObjectParts"] = GetObjectAttributesParts(
                TotalPartsCount=len(key.multipart.partlist)
            )
        return response
def validate_bucket_name(bucket: BucketName) -> None:
    """
    Validate s3 bucket name based on the documentation
    ref. https://docs.aws.amazon.com/AmazonS3/latest/userguide/bucketnamingrules.html
    """
    if not is_bucket_name_valid(bucket_name=bucket):
        ex = InvalidBucketName("The specified bucket is not valid.")
        ex.BucketName = bucket
        raise ex
def validate_canned_acl(canned_acl: str) -> None: