### 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
search_match = re.search(PATH_REGEX_RESPONSES, path)
    api_id = search_match.group(1)
    response_type = (search_match.group(2) or "").lstrip("/")
    if method == "GET":
        if response_type:
            return get_gateway_response(api_id, response_type)
        return get_gateway_responses(api_id)
    if method == "PUT":
        return put_gateway_response(api_id, response_type, data)
    if method == "PATCH":
        return update_gateway_response(api_id, response_type, data)
    if method == "DELETE":
        return delete_gateway_response(api_id, response_type)
    return make_error_response(
        "Not implemented for API Gateway gateway responses: %s" % method, code=404
    )
def to_authorizer_response_json(api_id, data):
    return to_response_json("authorizer", data, api_id=api_id)
def to_validator_response_json(api_id, data):
    return to_response_json("validator", data, api_id=api_id)
def to_documentation_part_response_json(api_id, data):