### 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_
subscription_list = aws_client.sns.list_subscriptions_by_topic(TopicArn=topic_arn)
            for subscription in subscription_list["Subscriptions"]:
                aws_client.sns.unsubscribe(SubscriptionArn=subscription["SubscriptionArn"])
            for server in servers:
                server.stop()
    @pytest.mark.aws_validated
    @pytest.mark.skip_snapshot_verify(paths=["$..Attributes.SubscriptionPrincipal"])
    def test_subscribe_sms_endpoint(self, sns_create_topic, sns_subscription, snapshot, aws_client):
        phone_number = "+123123123"
        topic_arn = sns_create_topic()["TopicArn"]
        response = sns_subscription(TopicArn=topic_arn, Protocol="sms", Endpoint=phone_number)
        snapshot.match("subscribe-sms-endpoint", response)
        sub_attrs = aws_client.sns.get_subscription_attributes(
            SubscriptionArn=response["SubscriptionArn"]
        )
        snapshot.match("subscribe-sms-attrs", sub_attrs)
    @pytest.mark.only_localstack
    def test_publish_sms_endpoint(self, sns_create_topic, sns_subscription, aws_client):
        list_of_contacts = [
            f"+{random.randint(100000000, 9999999999)}",
            f"+{random.randint(100000000, 9999999999)}",
            f"+{random.randint(100000000, 9999999999)}",
        ]
        message = "Good news everyone!"
        topic_arn = sns_create_topic()["TopicArn"]
        for number in list_of_contacts:
            sns_subscription(TopicArn=topic_arn, Protocol="sms", Endpoint=number)
        aws_client.sns.publish(Message=message, TopicArn=topic_arn)
        sns_backend = SnsProvider.get_store(TEST_AWS_ACCOUNT_ID, TEST_AWS_REGION_NAME)
        def check_messages():