### 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_
snapshot.match("sub-filter-policy-rule-no-list", e.value.response)
        assert (
            e.value.response["Error"]["Message"]
            == 'Invalid parameter: FilterPolicy: "key_a" must be an object or an array'
        )
    @pytest.mark.aws_validated
    @pytest.mark.parametrize("raw_message_delivery", [True, False])
    def test_filter_policy_on_message_body(
        self,
        sqs_create_queue,
        sns_create_topic,
        sns_create_s,
        snapshot,
        raw_message_delivery,
        aws_client,
    ):
        topic_arn = sns_create_topic()["TopicArn"]
        queue_url = sqs_create_queue()
        subscription = sns_create_s(topic_arn=topic_arn, queue_url=queue_url)
        subscription_arn = subscription["SubscriptionArn"]
        # s
        nested_filter_policy = {
            "object": {
                "key": [{"prefix": "auto-"}, "hardcodedvalue"],
                "nested_key": [{"exists": False}],
            },
            "test": [{"exists": False}],
        }
        aws_client.sns.set_subscription_attributes(
            SubscriptionArn=subscription_arn,