### 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_
"""
        external_url = external_service_url("sns")
        unsubscribe_url = create_unsubscribe_url(external_url, subscriber["SubscriptionArn"])
        message_attributes = prepare_message_attributes(message_context.message_attributes)
        event = {
            "Records": [
                {
                    "EventSource": "aws:sns",
                    "EventVersion": "1.0",
                    "EventSubscriptionArn": subscriber["SubscriptionArn"],
                    "Sns": {
                        "Type": message_context.type or "Notification",
                        "MessageId": message_context.message_id,
                        "TopicArn": subscriber["TopicArn"],
                        "Subject": message_context.subject,
                        "Message": message_context.message_content(subscriber["Protocol"]),
                        "Timestamp": timestamp_millis(),
                        "SignatureVersion": "1",
                        
                        
                        "Signature": "EXAMPLEpH+..",
                        "SigningCertUrl": "https://sns.us-east-1.amazonaws.com/SimpleNotificationService-0000000000000000000000.pem",
                        "UnsubscribeUrl": unsubscribe_url,
                        "MessageAttributes": message_attributes,
                    },
                }
            ]
        }
        return json.dumps(event)
class SqsTopicPublisher(TopicPublisher):