fix(pool): terminate workers on CTRL+c forceful exits

[AriPerkkio]

Description

Resolves #9123

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[hi-ogawa]

Looks good to me.

With execSync example #9123 (comment), CTRL+c x 2 seems to leave sleep 10s process becoming zombie, but I guess this is expected?

[AriPerkkio]

With execSync example #9123 (comment), CTRL+c x 2 seems to leave sleep 10s process becoming zombie, but I guess this is expected?

Yes. These changes will make sure the Vitest test runner worker is terminated. If the worker side is not fully blocked, I would expect Node to pass kill signals to any running code. execSync however blocks everything so there's nothing to do.

Minimal repro without Vitest. Top terminal runs the command, middle terminal shows processes matching example name, bottom terminal shows processes matching sleep command. Notice how example nested is left zombie after example main and example child terminate:

node-zombies.webm

repro code

import { execSync, fork } from "node:child_process";
import { setTimeout } from "node:timers/promises";
import { fileURLToPath } from "node:url";

const isMainThread = process.send === undefined;
const isChildProcess = process.send !== undefined;
const isNestedChildProcess = process.env.NESTED_CHILD_PROCESS;

if (isMainThread) {
  process.title = "example main";
  const child = fork(fileURLToPath(import.meta.url));

  await setTimeout(2_000);
  console.log("Terminating child process")
  child.kill();
}

if (isChildProcess && !isNestedChildProcess) {
  process.title = "example child";
  fork(fileURLToPath(import.meta.url), { env: { NESTED_CHILD_PROCESS: '1' }});
}

if (isNestedChildProcess) {
  process.title = "example nested";
  execSync("sleep 10s");
}