### 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_
continue
                messages_amount = len(filtered_messages)
                if messages_amount != messages_amount_before_filtering:
                    LOG.debug(
                        "After applying subscription filter, %s out of %s message(s) to be sent to '%s'",
                        messages_amount,
                        messages_amount_before_filtering,
                        subscriber["SubscriptionArn"],
                    )
                    
                    
                    subscriber_ctx = copy.copy(ctx)
                    subscriber_ctx.messages = filtered_messages
                LOG.debug(
                    "Topic '%s' batch publishing %s messages to subscribed '%s' with protocol '%s' (subscription '%s')",
                    topic_arn,
                    messages_amount,
                    subscriber.get("Endpoint"),
                    subscriber["Protocol"],
                    subscriber["SubscriptionArn"],
                )
                self.executor.submit(
                    notifier.publish, context=subscriber_ctx, subscriber=subscriber
                )
            else:
                
                notifier = self.topic_notifiers[subscriber["Protocol"]]
                for message in ctx.messages:
                    if self._should_publish(
                        ctx.store.subscription_filter_policy, message, subscriber