### 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_
moto_response = call_moto(context)
        subscription_arn = moto_response.get("SubscriptionArn")
        parsed_topic_arn = parse_and_validate_topic_arn(topic_arn)
        store = self.get_store(account_id=parsed_topic_arn["account"], region_name=context.region)
        
        
        for existing_topic_subscription in store.topic_subscriptions.get(topic_arn, []):
            sub = store.subscriptions.get(existing_topic_subscription, {})
            if sub.get("Endpoint") == endpoint:
                return SubscribeResponse(SubscriptionArn=sub["SubscriptionArn"])
        subscription = {
            
            "TopicArn": topic_arn,
            "Endpoint": endpoint,
            "Protocol": protocol,
            "SubscriptionArn": subscription_arn,
            "PendingConfirmation": "true",
            "Owner": context.account_id,
            "RawMessageDelivery": "false",  
        }
        if attributes:
            subscription.update(attributes)
            if "FilterPolicy" in attributes:
                store.subscription_filter_policy[subscription_arn] = json.loads(
                    attributes["FilterPolicy"]
                )
        store.subscriptions[subscription_arn] = subscription
        topic_subscription = store.topic_subscriptions.setdefault(topic_arn, [])
        topic_subscription.append(subscription_arn)