### 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 SQS Batch publisher is responsible for publishing batched SNS messages to a subscribed SQS queue using
    `SQS.send_message_batch`. This allows to make use of SQS batching capabilities.
    See https://docs.aws.amazon.com/sns/latest/dg/sns-batch-api-actions.html
    https://docs.aws.amazon.com/sns/latest/api/API_PublishBatch.html
    https://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/API_SendMessageBatch.html
    """
    def _publish(self, context: SnsBatchPublishContext, subscriber: SnsSubscription):
        entries = []
        sqs_system_attrs = create_sqs_system_attributes(context.request_headers)
        
        failure_map = {}
        for index, message_ctx in enumerate(context.messages):
            message_body = self.prepare_message(message_ctx, subscriber)
            sqs_message_attrs = self.create_sqs_message_attributes(
                subscriber, message_ctx.message_attributes
            )
            entry = {"Id": f"sns-batch-{index}", "MessageBody": message_body}
            
            failure_map[entry["Id"]] = {
                "context": message_ctx,
                "entry": entry,
            }
            if sqs_message_attrs:
                entry["MessageAttributes"] = sqs_message_attrs
            if message_ctx.message_group_id:
                entry["MessageGroupId"] = message_ctx.message_group_id
            if message_ctx.message_deduplication_id:
                entry["MessageDeduplicationId"] = message_ctx.message_deduplication_id