Fix express responses dying early

[heimskr]

What does this PR do?

Fixes ServerResponse.finished not being initialized to false on construction. This (sometimes) caused Express responses to never complete. (Fixed version of #18078)

• Documentation or TypeScript types
• Code changes

How did you verify your code works?

In addition to running the node:http tests, I ran this reproduction provided on Discord by @Lillious and spammed refresh with cache disabled on a simple index.html page that includes an image:

import express from "express";
import path from "path";
import http from "http";
const port = process.env.WEB_PORT || 8081;

const webserver = express();
webserver.use(express.json());
webserver.use(express.urlencoded({ extended: true }));
webserver.disable("x-powered-by");

webserver.use(express.static(path.join(import.meta.dir, "www")));

const server = http.createServer(webserver);

server.listen(port, () => {
  console.log(`Webserver is running on port ${port}`);
});

server.on("error", (error) => {
  console.error(error);
});

Before this fix, it would sometimes fail to load the image or the page itself. Now it always succeeds.

[robobun]

^{Updated 8:58 PM PT - Mar 11th, 2025}

✅ @heimskr, your commit 8ccdc4bc6428c3d650f223f62307ca738ef7a745 passed in Build #13078! 🎉

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🧪   try this PR locally:

bunx bun-pr 18080

[nektro]

node doesnt use a symbol but otherwise LGTM
a test would be nice but not strictly necessary to unblock