### 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
else:
                response = LambdaResponse()
                parsed_result = (
                    result if isinstance(result, dict) else json.loads(str(result or "{}"))
                )
                parsed_result = common.json_safe(parsed_result)
                parsed_result = {} if parsed_result is None else parsed_result
                response.status_code = int(parsed_result.get("statusCode", 200))
                parsed_headers = parsed_result.get("headers", {})
                if parsed_headers is not None:
                    response.headers.update(parsed_headers)
                try:
                    result_body = parsed_result.get("body")
                    if isinstance(result_body, dict):
                        response._content = json.dumps(result_body)
                    else:
                        body_bytes = to_bytes(to_str(result_body or ""))
                        if parsed_result.get("isBase64Encoded", False):
                            body_bytes = base64.b64decode(body_bytes)
                        response._content = body_bytes
                except Exception as e:
                    LOG.warning("Couldn't set Lambda response content: %s", e)
                    response._content = "{}"
                update_content_length(response)
                response.multi_value_headers = parsed_result.get("multiValueHeaders") or {}
            
            response._content = apply_template(integration, "response", response._content)
            response.headers["Content-Length"] = str(len(response.content or ""))
            return response
        raise Exception(