Reduce memory usage in long-running processes

[Jarred-Sumner]

What does this PR do?

New:

┌─────────────────────────┬──────────┐
│                         │ Values   │
├─────────────────────────┼──────────┤
│   Memory usage MB (RSS) │ 650      │
│ AbortSignal alive count │ 200002   │
│ new AbortSignal() calls │ 55500000 │
│        Uptime (seconds) │ 630      │
└─────────────────────────┴──────────┘

Previously:

┌─────────────────────────┬──────────┐
│                         │ Values   │
├─────────────────────────┼──────────┤
│   Memory usage MB (RSS) │ 678      │
│ AbortSignal alive count │ 495616   │
│ new AbortSignal() calls │ 55500000 │
│        Uptime (seconds) │ 630      │
└─────────────────────────┴──────────┘

For the following script:

console.clear();
console.log("Starting...");
const iterationCount = 100000;
globalThis.signals = new Array(iterationCount);
globalThis.requests = new Array(iterationCount);
var total = 0;
setInterval(() => {
  const rss = (process.memoryUsage.rss() / 1024 / 1024) | 0;
  const objectTypeCounts = require("bun:jsc").heapStats().objectTypeCounts;
  console.table({
    "Memory usage MB (RSS)": rss,
    "AbortSignal alive count": objectTypeCounts.AbortSignal || 0,
    "new AbortSignal() calls": total,
    "Uptime (seconds)": Math.floor(process.uptime()),
  });
}, 10000);
while (true) {
  for (let i = 0; i < iterationCount; i++) {
    const req = new Request("https://example.com/");
    requests[i] = req;
    signals[i] = AbortSignal.any([req.signal, new AbortController().signal]);
  }
  total += iterationCount;
  await Bun.sleep(1000);
}

How did you verify your code works?

CI

[robobun]

❌ @Jarred-Sumner, your commit bcab095 has 4 failures in #5403:

test/js/bun/http/serve.test.ts - 1 failing on 🍎 x64

test/js/web/fetch/fetch.tls.test.ts - 1 failing on 🍎 aarch64

test/js/web/websocket/websocket-client.test.ts - 2 failing on 🪟 x64

test/js/web/websocket/websocket-client.test.ts - 2 failing on 🪟 x64-baseline

test/cli/hot/hot.test.ts - 2 failing on 🪟 x64-baseline