### 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_
PlatformApplicationArn=app_arn, Token=short_uid()
        )["EndpointArn"]
        endpoint_arn_2 = aws_client.sns.create_platform_endpoint(
            PlatformApplicationArn=app_arn, Token=short_uid()
        )["EndpointArn"]
        sns_subscription(
            TopicArn=topic_arn,
            Protocol="application",
            Endpoint=endpoint_arn,
        )
        # e
        # h
        message = json.dumps({"APNS": json.dumps({"aps": {"content-available": 1}})})
        message_for_topic = {
            "default": "This is the default message which must be present when publishing a message to a topic.",
            "APNS": json.dumps({"aps": {"content-available": 1}}),
        }
        message_for_topic_string = json.dumps(message_for_topic)
        message_attributes = {
            "AWS.SNS.MOBILE.APNS.TOPIC": {
                "DataType": "String",
                "StringValue": "com.amazon.mobile.messaging.myapp",
            },
            "AWS.SNS.MOBILE.APNS.PUSH_TYPE": {
                "DataType": "String",
                "StringValue": "background",
            },
            "AWS.SNS.MOBILE.APNS.PRIORITY": {
                "DataType": "String",
                "StringValue": "5",