### 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_
"""
    The email-json publisher is responsible for publishing the SNS message to a subscribed email address.
    The format of the message will be JSON-encoded, and "is meant for applications to programmatically process emails".
    There is not a lot of AWS documentation on SNS emails.
    See https://docs.aws.amazon.com/sns/latest/dg/sns-email-notifications.html
    But it is mentioned several times in the SNS FAQ (especially in #Transports section):
    https://aws.amazon.com/sns/faqs/
    """
    def _publish(self, context: SnsPublishContext, subscriber: SnsSubscription):
        region = extract_region_from_arn(subscriber["Endpoint"])
        ses_client = connect_to(region_name=region).ses
        if endpoint := subscriber.get("Endpoint"):
            ses_client.verify_email_address(EmailAddress=endpoint)
            ses_client.verify_email_address(EmailAddress="admin@localstack.com")
            message_body = self.prepare_message(context.message, subscriber)
            ses_client.send_email(
                Source="admin@localstack.com",
                Message={
                    "Body": {"Text": {"Data": message_body}},
                    "Subject": {"Data": "SNS-Subscriber-Endpoint"},
                },
                Destination={"ToAddresses": [endpoint]},
            )
            store_delivery_log(context.message, subscriber, success=True)
class EmailTopicPublisher(EmailJsonTopicPublisher):