### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

`#return` macro for AppSync is not supported

```
- ["Error in template '<string>' at position 48-60 in expression: #return($v1)\nException: no such macro: return\n\nGraphQL request:3:11\n2 |         {\n3 |           hi2 {\n  |           ^\n4 |             value"] None
```

### Expected Behavior

`#return` is a valid command in AppSync Resolver Velocity request and response templates.

https://docs.aws.amazon.com/appsync/latest/devguide/aws-appsync-directives.html 

### How are you starting LocalStack?

With the `localstack` script

### Steps To Reproduce

#### How are you starting localstack (e.g., `bin/localstack` command, arguments, or `docker-compose.yml`)

    localstack start

#### Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)

1. `CDKDeployment`
2. GraphQL Rest API to `localstack`

3. AppSync resolver with response template:

```vtl
#set($v1 = {})
$util.qr($v1.put('value', 'hi'))
#return($v1)"
```

```sdl
schema {
  query: Query
}
type valueObj {
  value: String
}
type Query {
  hi2: valueObj
}
```

4. Query AppSync

```sdl
Query {
   hi2
}
```



### Environment

```markdown
- OS: Ubuntu/WSL2
- LocalStack: 0.14.2.1
```


### Anything else?

The same code runs fine on AWS/AppSync.
"""Abstract base class representing a backend integration"""
class SnsIntegration(BackendIntegration):
    @classmethod
    def invoke(cls, invocation_context: ApiInvocationContext):
        try:
            request_templates = RequestTemplates()
            payload = request_templates.render(invocation_context)
        except Exception as e:
            LOG.warning("Failed to apply template for SNS integration", e)
            raise
        uri = (
            invocation_context.integration.get("uri")
            or invocation_context.integration.get("integrationUri")
            or ""
        )
        region_name = uri.split(":")[3]
        headers = aws_stack.mock_aws_request_headers(service="sns", region_name=region_name)
        return make_http_request(
            config.service_url("sns"), method="POST", headers=headers, data=payload
        )
class VelocityUtil:
    """
    Simple class to mimic the behavior of variable '$util' in AWS API Gateway integration
    velocity templates.
    See: http://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-mapping-template-reference.html
    """
    def base64Encode(self, s):