### 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
env = get_environment(env)
    
    conn = connect_to_service("sqs", env=env)
    return conn.create_queue(QueueName=queue_name)
def sqs_queue_arn(queue_name, account_id=None, region_name=None):
    account_id = get_account_id(account_id)
    region_name = region_name or get_region()
    queue_name = queue_name.split("/")[-1]
    return "arn:aws:sqs:%s:%s:%s" % (region_name, account_id, queue_name)
def apigateway_restapi_arn(api_id, account_id=None, region_name=None):
    account_id = get_account_id(account_id)
    region_name = region_name or get_region()
    return "arn:aws:apigateway:%s:%s:/restapis/%s" % (region_name, account_id, api_id)
def sqs_queue_name(queue_arn):
    if ":" in queue_arn:
        return parse_arn(queue_arn)["resource"]
    else:
        return queue_arn
def sns_topic_arn(topic_name, account_id=None):
    account_id = get_account_id(account_id)
    return "arn:aws:sns:%s:%s:%s" % (get_region(), account_id, topic_name)
def sqs_receive_message(queue_arn):
    region_name = extract_region_from_arn(queue_arn)
    client = connect_to_service("sqs", region_name=region_name)
    queue_url = get_sqs_queue_url(queue_arn)
    response = client.receive_message(QueueUrl=queue_url)
    return response
def firehose_name(firehose_arn):