### 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_
MessageAttributeNames=["All"],
            VisibilityTimeout=0,
            WaitTimeSeconds=4,
        )
        snapshot.match("message-raw-true", response)
        # f
        assert response["Messages"][0]["MessageAttributes"] == {
            "attr1": {"DataType": "Number", "StringValue": string_value}
        }
        aws_client.sqs.delete_message(
            QueueUrl=queue_url, ReceiptHandle=response["Messages"][0]["ReceiptHandle"]
        )
        aws_client.sns.set_subscription_attributes(
            SubscriptionArn=subscription_arn,
            AttributeName="RawMessageDelivery",
            AttributeValue="false",
        )
        response = aws_client.sns.get_subscription_attributes(SubscriptionArn=subscription_arn)
        snapshot.match("sub-attrs-raw-false", response)
        string_value = "100.12"
        aws_client.sns.publish(
            TargetArn=topic_arn,
            Message="Test msg",
            MessageAttributes={"attr1": {"DataType": "Number", "StringValue": string_value}},
        )
        response = aws_client.sqs.receive_message(
            QueueUrl=queue_url,
            MessageAttributeNames=["All"],
            VisibilityTimeout=0,
            WaitTimeSeconds=4,