This follows the pattern for the other services spawned by WebContent.
The notable quirk about this service is that it's actually spawned by
the ImageCodecPlugin rather than in main.cpp in the non-Android port.
As a result we needed to do some ifdef surgery to get all the pieces
in place. But we can now load images in the Android port again :^).
Similar to the RequestServer, bind this from the WebContentService
implementation and have it work the same way. Deduplicate some code
while we're here.
Add a RequestServerService class that uses the LadybirdServiceBase class
added previously. Bind to it from the WebContentService's service_main()
during startup.
Create LadybirdServiceBase to hold the standard "set resource dir" and
"init ipc sockets" service functionality that will be common between the
WebContent, RequestServer, and WebSocket services.
Refactor the handler class slightly to avoid the HandlerLeak lint by
making the class a static class inside the companion object and use a
WeakReference to the service instead of a strong one.
