### 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_
self, message_context: SnsMessage, subscriber: SnsSubscription
    ) -> Union[str, Dict]:
        endpoint_arn = subscriber["Endpoint"]
        platform_type = get_platform_type_from_endpoint_arn(endpoint_arn)
        return {
            "TargetArn": endpoint_arn,
            "TopicArn": subscriber["TopicArn"],
            "SubscriptionArn": subscriber["SubscriptionArn"],
            "Message": message_context.message_content(protocol=platform_type),
            "MessageAttributes": message_context.message_attributes,
            "MessageStructure": message_context.message_structure,
            "Subject": message_context.subject,
        }
    @staticmethod
    def _legacy_publish_to_gcm(context: SnsPublishContext, endpoint: str):
        application_attributes, endpoint_attributes = get_attributes_for_application_endpoint(
            endpoint
        )
        send_message_to_gcm(
            context=context,
            app_attributes=application_attributes,
            endpoint_attributes=endpoint_attributes,
        )
class SmsTopicPublisher(TopicPublisher):