### 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_
from localstack.services.sns.provider import SnsProvider
from localstack.testing.aws.util import is_aws_cloud
from localstack.utils import testutil
from localstack.utils.aws.arns import parse_arn
from localstack.utils.net import wait_for_port_closed, wait_for_port_open
from localstack.utils.strings import short_uid, to_str
from localstack.utils.sync import poll_condition, retry
from localstack.utils.testutil import check_expected_lambda_log_events_length
from .awslambda.functions import lambda_integration
from .awslambda.test_lambda import TEST_LAMBDA_PYTHON, TEST_LAMBDA_PYTHON_ECHO
LOG = logging.getLogger(__name__)
PUBLICATION_TIMEOUT = 0.500
PUBLICATION_RETRIES = 4
@pytest.fixture(autouse=True)
def sns_snapshot_transformer(snapshot):
    snapshot.add_transformer(snapshot.transform.sns_api())
    
    
    snapshot.add_transformer(
        snapshot.transform.key_value(
            "SubscriptionPrincipal",
            value_replacement="<sub-principal>",
            reference_replacement=False,
        ),
        priority=-1,
    )
@pytest.fixture
def sns_create_platform_application(aws_client):
    platform_applications = []
    def factory(**kwargs):