### 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_
context: SnsPublishContext, app_attributes: Dict[str, str], endpoint_attributes: Dict[str, str]
) -> None:
    """
    Send the message directly to GCM, with the credentials used when creating the PlatformApplication and the Endpoint
    :param context: SnsPublishContext
    :param app_attributes: ApplicationPlatform attributes, contains PlatformCredential for GCM
    :param endpoint_attributes: Endpoint attributes, contains Token that represent the mobile endpoint
    :return:
    """
    server_key = app_attributes.get("PlatformCredential", "")
    token = endpoint_attributes.get("Token", "")
    
    json_message = context.message.message_content("GCM")
    data = json.loads(json_message)
    data["to"] = token
    headers = {"Authorization": f"key={server_key}", "Content-type": "application/json"}
    response = requests.post(
        sns_constants.GCM_URL,
        headers=headers,
        data=json.dumps(data),
    )
    if response.status_code != 200:
        LOG.warning(
            f"Platform GCM returned response {response.status_code} with content {response.content}"
        )
def create_sns_message_body(message_context: SnsMessage, subscriber: SnsSubscription) -> str: