Add http.serve() API based on Fetch (Request -> Response)

What is the problem this feature will solve?

Node provides fetch, Request/Response, and Web Streams, but no high level server API using this model.

Other runtimes such as Deno and Bun expose a serve API based on the Fetch contract. In Node, similar patterns are commonly implemented in userland (e.g., frameworks like Hono), which indicates demand for this abstraction.

This was discussed in #42529 and received support, however that issue is focused on request.toWeb(), so opening a separate issue focused on this API.

What is the feature you are proposing to solve the problem?

Add a high-level http.serve(handler) API.

An example shape could be:

http.serve((req) => new Response("ok"))

handler: (Request) => Response | Promise<Response>

This would coexist with the existing http.createServer, and be a high level alternative using WHATWG APIs instead.

What alternatives have you considered?

• Continue using http.createServer directly.
• Implement this in userland, or use existing 3rd party solutions.

Start by reviewing Node's existing http.createServer API and the discussion in issue #42529. The proposed work is to define and add http.serve(handler) using Request and Response while keeping createServer available. Done means the API shape and behavior are agreed, implemented, and covered for synchronous and asynchronous handlers.