Add a modern HTTP server API that uses the Fetch API's Request and
Response objects, bypassing the legacy IncomingMessage/ServerResponse
stream-based model.

Features:
- serve(options, handler) creates HTTP or HTTPS servers
- Handler receives Request, returns Response (sync or async)
- getRemoteMetadata(request) retrieves connection info
- Automatic chunked transfer encoding when no Content-Length
- Keep-alive connection support
- Graceful shutdown via AbortSignal
- Custom error handling via onError callback

The implementation reuses the battle-tested HTTPParser but creates
Fetch API objects directly from parser output. Requests are serialized
per connection (no HTTP pipelining) - parser is paused after headers
and resumed after response is written.

Example usage:
  const { serve, getRemoteMetadata } = require('http');

  const server = serve({}, async (request) => {
    const body = await request.json();
    return Response.json({ received: body });
  });
  server.listen(3000);