### 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_
return ConfirmSubscriptionResponse(SubscriptionArn=subscription_arn)
        subscription["PendingConfirmation"] = "false"
        subscription["ConfirmationWasAuthenticated"] = "true"
        return ConfirmSubscriptionResponse(SubscriptionArn=subscription_arn)
    def untag_resource(
        self, context: RequestContext, resource_arn: AmazonResourceName, tag_keys: TagKeyList
    ) -> UntagResourceResponse:
        call_moto(context)
        
        store = self.get_store(context.account_id, context.region)
        existing_tags = store.sns_tags.setdefault(resource_arn, [])
        store.sns_tags[resource_arn] = [t for t in existing_tags if t["Key"] not in tag_keys]
        return UntagResourceResponse()
    def list_tags_for_resource(
        self, context: RequestContext, resource_arn: AmazonResourceName
    ) -> ListTagsForResourceResponse:
        
        store = self.get_store(context.account_id, context.region)
        tags = store.sns_tags.setdefault(resource_arn, [])
        return ListTagsForResourceResponse(Tags=tags)
    def create_platform_application(
        self, context: RequestContext, name: String, platform: String, attributes: MapStringToString
    ) -> CreatePlatformApplicationResponse:
        
        
        
        
        
        return call_moto(context)
    def create_platform_endpoint(