### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

Currently the VTL template for `request_templates` is not processed properly:

```
#set( $body = $input.json("$") )

#macro( loop $map )
{
    #foreach($key in $map.keySet())
        #set( $k = $util.escapeJavaScript($key) )
        #set( $v = $util.escapeJavaScript($map.get($key)).replaceAll("\\'", "'") )
        "$k": "$v"
        #if( $foreach.hasNext ) , #end
    #end
}
#end

{
    "enhancedAuthContext": #loop($context.authorizer),

    "headers": #loop($input.params().header),

    "query": #loop($input.params().querystring),

    "path": #loop($input.params().path),

    "identity": #loop($context.identity),

    "stageVariables": #loop($stageVariables),
}
EOF
}
```

results in,

```
'

{
    "enhancedAuthContext": {
    }
,

    "headers": {
    }
,

    "query": {
    }
,

    "path": {
    }
,

    "identity": {
    }
,

    "stageVariables": {
    }
,
}
'
```

### Expected Behavior

The template should be rendered and have the JSON properties.

### How are you starting LocalStack?

Custom (please describe below)

### Steps To Reproduce

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

    docker run localstack/localstack

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

    awslocal s3 mb s3://mybucket


### Environment

```markdown
- OS: MacOS
- LocalStack: 0.14
```


### Anything else?

This example can be used to validate.
https://github.com/localstack/localstack-terraform-samples/tree/master/apigateway-lambda-velocity
headers = aws_stack.mock_aws_request_headers(
                service="kinesis", region_name=invocation_context.region_name
            )
            headers["X-Amz-Target"] = target
            result = common.make_http_request(
                url=config.service_url("kineses"), data=payload, headers=headers, method="POST"
            )
            
            result = apply_request_response_templates(
                result, response_templates, content_type=APPLICATION_JSON
            )
            return result
        elif "states:action/" in uri:
            action = uri.split("/")[-1]
            if APPLICATION_JSON in integration.get("requestTemplates", {}):
                payload = apply_request_response_templates(
                    data,
                    integration.get("requestTemplates"),
                    content_type=APPLICATION_JSON,
                    as_json=True,
                )
            else:
                payload = json.loads(data.decode("utf-8"))
            client = aws_stack.connect_to_service("stepfunctions")
            if isinstance(payload.get("input"), dict):
                payload["input"] = json.dumps(payload["input"])
            
            method_name = (
                camel_to_snake_case(action) if action != "StartSyncExecution" else "start_execution"
            )