### 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_
)
        sub_attrs = aws_client.sns.get_subscription_attributes(SubscriptionArn=subscription_arn)
        snapshot.match("subscriptions-attrs", sub_attrs)
        message = "test_dlq_before_sqs_endpoint_deleted"
        aws_client.sns.publish(TopicArn=topic_arn, Message=message)
        response = aws_client.sqs.receive_message(
            QueueUrl=queue_url, WaitTimeSeconds=10, MaxNumberOfMessages=4
        )
        snapshot.match("messages-before-delete", response)
        aws_client.sqs.delete_message(
            QueueUrl=queue_url, ReceiptHandle=response["Messages"][0]["ReceiptHandle"]
        )
        aws_client.sqs.delete_queue(QueueUrl=queue_url)
        # s
        # h
        queue_test_url = sqs_create_queue()
        test_subscription = sns_create_s(
            topic_arn=topic_arn, queue_url=queue_test_url
        )
        test_subscription_arn = test_subscription["SubscriptionArn"]
        # t
        message = "test_dlq_after_sqs_endpoint_deleted"
        aws_client.sns.publish(TopicArn=topic_arn, Message=message)
        # t
        # w
        poll_condition(
            lambda: sqs_receive_num_messages(
                queue_url=queue_test_url, expected_messages=1, max_iterations=2
            ),
            timeout=10,