WikiNodeCdnWarmer: Add ability to also warm any aggregated assets for a request

[Ambient-Impact]

Currently, only the HTML response is warmed since it's using Guzzle rather than a browser, so the former does not attempt to load any referenced stylesheets and JavaScript files like a browser would (to my knowledge). It would be possible to parse the response into a DOM that can be searched to find the appropriate elements, but that could be a security issue if we assume the content is trusted when it may have been tampered with.

A better and more secure solution would remove the need for a round trip over the network and instead get a list of aggregates from the database. It doesn't look like there's a complete list of aggregates in cache or state (though some JS in state), so what we could do is to save that information in cache when aggregate URLs are generated, and then retrieve those from cache (in a second warmer plug-in?) and request them.