Make AbortSignal.timeout() 6x faster

[Jarred-Sumner]

What does this PR do?

This makes it so the only usage of us_create_timer is the sweep and date timers used by us_loop_t. The GC timers and AbortSignal.timeout use the timer heap. This will have memory usage implications so we need to measure memory usage changes in some scenarios before merging this.

This also switches the list of pending fetch() calls to shutdown to a HashMap instead of an ArrayHashMap, and swaps the multi-threaded queue of shutdowns

Stress test below gets 10x faster:

❯ mem bun ~/Desktop/signals.js
[196.05ms] [100000x] fetch(url, { signal })
[239.94ms] [100000x] await Promise.all(promises)

Peak memory usage: 509 MB

❯ mem bun-1.1.36 ~/Desktop/signals.js
[2.19s] [100000x] fetch(url, { signal })
[4.66s] [100000x] await Promise.all(promises)

Peak memory usage: 503 MB

Code:

const count = 100_000;
import { createServer } from "http";

const server = createServer((req, res) => {
  res.end("Hello, world!");
});

const promises = new Array(count);
const listenPromise = Promise.withResolvers();

server.listen(0, () => {
  listenPromise.resolve();
});
await listenPromise.promise;
const port = server.address().port;

console.time("[" + count + "x] " + "fetch(url, { signal })");
for (let i = 0; i < count; i++) {
  const signal = AbortSignal.timeout(1);
  promises[i] = fetch(`http://localhost:${port}`, {
    signal,
  }).catch(() => {});
}
console.timeEnd("[" + count + "x] " + "fetch(url, { signal })");

console.time("[" + count + "x] " + "await Promise.all(promises)");
await Promise.all(promises);
console.timeEnd("[" + count + "x] " + "await Promise.all(promises)");

server.close();

How did you verify your code works?

[robobun]

❌ @dylan-conway, your commit 35d16be has some failures in #6860