### Is there an existing issue for this?

- [X] I have searched the existing issues

### Feature description

SNS allows for the publishing of messages to an SMS destination with a phone number. Those messages are logged and stored in the `SnsStore`, but there is no way to retrieve them for verification. The request here is to expose a new endpoint which returns SMS messages from the store, similar to the one made available to retrieve email messages sent via SES.

### 🧑‍💻 Implementation

The `SNSServicePlatformEndpointMessagesApiResource` class makes endpoints available for accessing platform endpoint messages sent via SNS. A similar resource class could be implemented to provide new endpoints for accessing SMS messages.

Given that interaction platform endpoint messages is exposed at the path `/_aws/sns/platform-endpoint-messages`, SMS message interaction would presumably be exposed at `/_aws/sns/sms-messages`. A `GET` endpoint could accept an optional `phoneNumber` query parameter to filter messages based on the destination phone number.

```python
class SNSServiceSMSMessagesApiResource:
  @route(sns_constants.SMS_MSGS_ENDPOINT, methods=["GET"])
    def on_get(self, request: Request):
      account_id = #...
      region = #...
      filter_phone_number = request.args.get("phoneNumber")
      # get store; conditionally filter messages based on filter_phone_number
```

### Anything else?

_No response_
)
        sns_allow_topic_sqs_queue(
            sqs_queue_url=dlq_url,
            sqs_queue_arn=dlq_arn,
            sns_topic_arn=topic_arn,
        )
        aws_client.sqs.delete_queue(QueueUrl=queue_url)
        # A
        assert poll_condition(lambda: not sqs_queue_exists(queue_url), timeout=5)
        message = "test_dlq_after_sqs_endpoint_deleted"
        message_attr = {
            "attr1": {
                "DataType": "Number",
                "StringValue": "111",
            },
            "attr2": {
                "DataType": "Binary",
                "BinaryValue": b"\x02\x03\x04",
            },
        }
        aws_client.sns.publish(TopicArn=topic_arn, Message=message, MessageAttributes=message_attr)
        response = aws_client.sqs.receive_message(
            QueueUrl=dlq_url,
            WaitTimeSeconds=10,
            AttributeNames=["All"],
            MessageAttributeNames=["All"],
        )
        snapshot.match("messages", response)
    @pytest.mark.aws_validated
    def test_message_attributes_not_missing(