### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

I am running an SNS topic that publishes to a lambda function. The localstack code reads a type byte object from the lambda function invocation payload [here](https://github.com/localstack/localstack/blob/master/localstack/services/sns/publisher.py#L187) and then tries to dump the result into json [here](https://github.com/localstack/localstack/blob/master/localstack/services/sns/publisher.py#L863) which results in the following error:
```
sns_pub_0] l.services.sns.publisher   : Unable to run Lambda function on SNS message: Object of type bytes is not JSON serializable
```

### Expected Behavior

The payload bytes should be converted to a string before being dumped to json. The error should not be thrown.

### How are you starting LocalStack?

With a docker-compose file

### Steps To Reproduce

#### How are you starting localstack (e.g., `bin/localstack` command, arguments, or `docker-compose.yml`)

docker-compose up
(Using the standard docker-compose.yaml)

#### Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)

```
awslocal sns publish --message file://sns/message.json --topic-arn arn:aws:sns:us-east-1:000000000000:<topic_name>
```

### Environment

```markdown
- OS: macOS Ventura 13.2.1
- LocalStack: latest
```


### Anything else?

_No response_
"""
    The application publisher is responsible for publishing the SNS message to a subscribed SNS application endpoint.
    The SNS application endpoint represents a mobile app and device.
    The application endpoint can be of different types, represented in `SnsApplicationPlatforms`.
    This is not directly implemented yet in LocalStack, we save the message to be retrieved later from an internal
    endpoint.
    The `LEGACY_SNS_GCM_PUBLISHING` flag allows direct publishing to the GCM platform, with some caveats:
    - It always publishes if the platform is GCM, and raises an exception if the credentials are wrong.
    - the Platform Application should be validated before and not while publishing
    See https://docs.aws.amazon.com/sns/latest/dg/sns-mobile-application-as-subscriber.html
    """
    def _publish(self, context: SnsPublishContext, subscriber: SnsSubscription):
        endpoint_arn = subscriber["Endpoint"]
        message = self.prepare_message(context.message, subscriber)
        cache = context.store.platform_endpoint_messages[endpoint_arn] = (
            context.store.platform_endpoint_messages.get(endpoint_arn) or []
        )
        cache.append(message)
        if (
            config.LEGACY_SNS_GCM_PUBLISHING
            and get_platform_type_from_endpoint_arn(endpoint_arn) == "GCM"
        ):
            self._legacy_publish_to_gcm(context, endpoint_arn)
        
        
        store_delivery_log(context.message, subscriber, success=True)
    def prepare_message(