### 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_
"""
        Base method for publishing the message. It is up to the child class to implement its way to publish the message
        :param context: the SnsPublishContext created by the caller, containing the necessary data to publish the
        message
        :param endpoint: the endpoint where the message should be published
        :return:
        """
        raise NotImplementedError
    def prepare_message(self, message_context: SnsMessage, endpoint: str) -> str:
        """
        Base method to format the message. It is up to the child class to implement it.
        :param message_context: the SnsMessage containing the message data
        :param endpoint: the endpoint where the message should be published
        :return: the formatted message
        """
        raise NotImplementedError
class LambdaTopicPublisher(TopicPublisher):
    """
    The Lambda publisher is responsible for invoking a subscribed lambda function to process the SNS message using
    `Lambda.invoke` with the formatted message as Payload.
    See: https://docs.aws.amazon.com/lambda/latest/dg/with-sns.html
    """
    def _publish(self, context: SnsPublishContext, subscriber: SnsSubscription):
        try:
            lambda_client = aws_stack.connect_to_service(
                "lambda", region_name=extract_region_from_arn(subscriber["Endpoint"])
            )
            event = self.prepare_message(context.message, subscriber)