### 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_
@pytest.mark.only_localstack
    @pytest.mark.parametrize("raw_message_delivery", [True, False])
    def test_dlq_external_http_endpoint(
        self,
        sns_client,
        sqs_client,
        sns_create_topic,
        sqs_create_queue,
        sqs_queue_arn,
        sns_subscription,
        sns_create_http_endpoint,
        sns_create_s,
        sns_allow_topic_sqs_queue,
        raw_message_delivery,
    ):
        # N
        topic_arn, http_subscription_arn, endpoint_url, server = sns_create_http_endpoint(
            raw_message_delivery
        )
        dlq_url = sqs_create_queue()
        dlq_arn = sqs_queue_arn(dlq_url)
        sns_allow_topic_sqs_queue(
            sqs_queue_url=dlq_url, sqs_queue_arn=dlq_arn, sns_topic_arn=topic_arn
        )
        sns_client.set_subscription_attributes(
            SubscriptionArn=http_subscription_arn,
            AttributeName="RedrivePolicy",
            AttributeValue=json.dumps({"deadLetterTargetArn": dlq_arn}),
        )
        assert poll_condition(