### 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
nt
        if root and not root.tail:
            root.tail = "\n"
class SqsResponseSerializer(QueryResponseSerializer):
    """
    Unfortunately, SQS uses a rare interpretation of the XML protocol: It uses HTML entities within XML tag text nodes.
    For example:
    - Normal XML serializers: <Message>No need to escape quotes (like this: ") with HTML entities in XML.</Message>
    - SQS XML serializer: <Message>No need to escape quotes (like this: &quot;) with HTML entities in XML.</Message>
    None of the prominent XML frameworks for python allow HTML entity escapes when serializing XML.
    This serializer implements the following workaround:
    - Escape quotes and \r with their HTML entities (&quot; and &#xD;).
    - Since & is (correctly) escaped in XML, the serialized string contains &amp;quot; and &amp;#xD;
    - These double-escapes are corrected by replacing such strings with their original.
    """
    def _default_serialize(self, xmlnode: ETree.Element, params: str, _, name: str, __) -> None:
        """Ensures that XML text nodes use HTML entities instead of " or \r"""
        node = ETree.SubElement(xmlnode, name)
        node.text = str(params).replace('"', "&quot;").replace("\r", "&#xD;")
    def _node_to Optional[ETree.ElementTree], mime_type: str) -> Optional[str]:
        """
        Replaces the double-escaped HTML entities with their correct HTML entity (basically reverts the escaping in
        the serialization of the used XML framework).
        """
        generated_string = super()._node_to_string(pe)
        return (
            to_bytes(
                to_str(generated_string)
                # Undo the second escaping of the &
                .replace("&amp;quot;", "&quot;")
                # Undo the second escaping of the carriage return (\r)
                .replace("&amp;#xD;", "&#xD;")
            )
            if generated_string is not None
            else None
        )
def gen_amzn_requestid_long():
    return "".join([rando