### 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_
"""Provides a REST API for retrospective access to platform endpoint messages sent via SNS.
    This is registered as a LocalStack internal HTTP resource.
    This endpoint accepts:
    - GET param `accountId`: selector for AWS account. If not specified, return fallback `000000000000` test ID
    - GET param `region`: selector for AWS `region`. If not specified, return default "us-east-1"
    - GET param `endpointArn`: filter for `endpointArn` resource in SNS
    - DELETE param `accountId`: selector for AWS account
    - DELETE param `region`: will delete saved messages for `region`
    - DELETE param `endpointArn`: will delete saved messages for `endpointArn`
    """
    @route(sns_constants.PLATFORM_ENDPOINT_MSGS_ENDPOINT, methods=["GET"])
    def on_get(self, request: Request):