### 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
if method == "POST":
            if uri.startswith("arn:aws:apigateway:") and ":sqs:path" in uri:
                template = integration["requestTemplates"][APPLICATION_JSON]
                account_id, queue = uri.split("/")[-2:]
                region_name = uri.split(":")[3]
                if "GetQueueUrl" in template or "CreateQueue" in template:
                    new_request = (
                        f"{aws_stack.render_velocity_template(template, data)}&QueueName={queue}"
                    )
                else:
                    queue_url = f"{config.get_edge_url()}/{account_id}/{queue}"
                    new_request = (
                        f"{aws_stack.render_velocity_template(template, data)}&QueueUrl={queue_url}"
                    )
                headers = aws_stack.mock_aws_request_headers(service="sqs", region_name=region_name)
                url = urljoin(config.service_url("sqs"), f"{TEST_AWS_ACCOUNT_ID}/{queue}")
                result = common.make_http_request(
                    url, method="POST", headers=headers, data=new_request
                )
                return result
            elif uri.startswith("arn:aws:apigateway:") and ":sns:path" in uri:
                integration_response = SnsIntegration(invocation_context).invoke()
                return apply_request_response_templates(
                    integration_response, response_templates, content_type=APPLICATION_JSON
                )
        raise Exception(
            'API Gateway AWS integration action URI "%s", method "%s" not yet implemented'
            % (uri, method)
        )
    elif integration_type == "AWS_PROXY":