### 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_
PublishResponse,
    SnsApi,
    String,
    SubscribeResponse,
    SubscriptionAttributesMap,
    TagKeyList,
    TagList,
    TagResourceResponse,
    TooManyEntriesInBatchRequestException,
    TopicAttributesMap,
    UntagResourceResponse,
    attributeName,
    attributeValue,
    authenticateOnUnsubscribe,
    boolean,
    messageStructure,
    subscriptionARN,
    topicARN,
    topicName,
)
from localstack.http import Request, Response, Router, route
from localstack.services.edge import ROUTER
from localstack.services.moto import call_moto
from localstack.services.plugins import ServiceLifecycleHook
from localstack.services.sns import constants as sns_constants
from localstack.services.sns.models import SnsMessage, SnsStore, sns_stores
from localstack.services.sns.publisher import (
    PublishDispatcher,
    SnsBatchPublishContext,
    SnsPublishContext,