### 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
m.choice(REQUEST_ID_CHARACTERS) for _ in range(0, 52)])
def create_serializer(service: ServiceModel) -> ResponseSerializer:
    """
    Creates the right serializer for the given service model.
    :param service: to create the serializer for
    :return: ResponseSerializer which can handle the protocol of the service
    """
    # Unfortunately, some services show subtle differences in their serialized responses, even though their
    # specification states they implement the same protocol.
    # Since some clients might be stricter / less resilient than others, we need to mimic the serialization of the
    # specific services as close as possible.
    # Therefore, the service-specific seriallly more specific
    # protocol implementation) has precedence over the more general protocol-specific serializers.
    service_specific_serializers = {"sqs": SqsResponseSerializer, "s3": S3ResponseSerializer}
    protocol_specific_serializers = {
        "query": QueryResponseSerializer,
        "json": JSONResponseSerializer,
        "rest-json": RestJSONResponseSerializer,
        "rest-xml": RestXMLResponseSerializer,
        "ec2": EC2ResponseSerializer,
    }
    # Try to select a service-specific serializer implementation
    if service.service_name in service_specific_serializers:
        return service_specific_serializers[service.service_name]()
    else:
        # Otherwise, pick the protocol-specific serializer for the protocol of the service
        return protocol_specific_serializers[service.protocol]()
def aws_response_serializer(service: str, operation: str):
    """
    A decorator for an HTTP route that can serialize return values or exceptions into AWS responses.
    This can be used to create AWS request handlers in a convenient way. Example usage::
        from localstack.http import route, Request
        from localstack.aws.api.sqs import ListQueuesResult
        @route("/_aws/sqs/queues")
        @aws_response_serializer("sqs", "ListQueues")
        de