test: improve test-gc-http-client-timeout

test-gc-http-client-timeout is resource-intensive. It times out a lot on
CI. Move to sequential.

Approved for fast-tracking by:
Anna Henningsen <anna@addaleax.net>
Daniel Bevenius <daniel.bevenius@gmail.com>

PR-URL: https://github.com/nodejs/node/pull/23088
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

test/sequential/test-gc-http-client-timeout.js

@@ -0,0 +1,69 @@
+'use strict';
+// Flags: --expose-gc
+// just like test-gc-http-client.js,
+// but with a timeout set
+
+require('../common');
+const onGC = require('../common/ongc');
+
+function serverHandler(req, res) {
+  setTimeout(function() {
+    req.resume();
+    res.writeHead(200);
+    res.end('hello\n');
+  }, 100);
+}
+
+const http = require('http');
+const todo = 550;
+let done = 0;
+let count = 0;
+let countGC = 0;
+
+console.log(`We should do ${todo} requests`);
+
+const server = http.createServer(serverHandler);
+server.listen(0, getall);
+
+function getall() {
+  if (count >= todo)
+    return;
+
+  (function() {
+    function cb(res) {
+      res.resume();
+      done += 1;
+    }
+
+    const req = http.get({
+      hostname: 'localhost',
+      pathname: '/',
+      port: server.address().port
+    }, cb);
+
+    req.setTimeout(10, function() {
+      console.log('timeout (expected)');
+    });
+
+    count++;
+    onGC(req, { ongc });
+  })();
+
+  setImmediate(getall);
+}
+
+for (let i = 0; i < 10; i++)
+  getall();
+
+function ongc() {
+  countGC++;
+}
+
+setInterval(status, 100).unref();
+
+function status() {
+  global.gc();
+  console.log('Done: %d/%d', done, todo);
+  console.log('Collected: %d/%d', countGC, count);
+  if (countGC === todo) server.close();
+}