### 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
data: Union[Response, bytes],
    templates: Dict[str, str],
    content_type: str = None,
    as_json: bool = False,
):
    """Apply the matching request/response template (if it exists) to the payload data and return the result"""
    content_type = content_type or APPLICATION_JSON
    is_response = isinstance(data, Response)
    templates = templates or {}
    template = templates.get(content_type)
    if not template:
        return data
    content = (data.content if is_response else data) or ""
    result = aws_stack.render_velocity_template(template, content, as_json=as_json)
    if is_response:
        data._content = result
        update_content_length(data)
        return data
    return result
def is_test_invoke_method(method, path):
    return method == "POST" and bool(re.match(PATH_REGEX_TEST_INVOKE_API, path))
UPDATE_APIGATEWAY = ProxyListenerApiGateway()