### 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_
queue_url = sqs_create_queue()
        # c
        subscription = sns_create_s(topic_arn=topic_arn, queue_url=queue_url)
        filter_policy = {"attr1": [{"numeric": [">", 0, "<=", 100]}]}
        aws_client.sns.set_subscription_attributes(
            SubscriptionArn=subscription["SubscriptionArn"],
            AttributeName="FilterPolicy",
            AttributeValue=json.dumps(filter_policy),
        )
        response_attributes = aws_client.sns.get_subscription_attributes(
            SubscriptionArn=subscription["SubscriptionArn"],
        )
        snapshot.match("subscription-attributes", response_attributes)
        # p
        message = "This is a test message"
        aws_client.sns.publish(
            TopicArn=topic_arn,
            Message=message,
            MessageAttributes={"attr1": {"DataType": "Number", "StringValue": "99.12"}},
        )
        # a
        response = aws_client.sqs.receive_message(
            QueueUrl=queue_url,
            VisibilityTimeout=0,
            MessageAttributeNames=["All"],
            WaitTimeSeconds=4,
        )
        snapshot.match("messages", response)
    @pytest.mark.only_localstack
    def test_subscribe_platform_endpoint(