Set QUnit preconfig autostart to false to ensure qunit waits correctly for top level await in app

[evoactivity]

Without this when using top level await in your app the tests will break.

[test:ember] not ok 1 Chrome 131.0 - [undefined ms] - Global error: Uncaught Error: Called start() while test already started running at http://localhost:7357/assets/tests-BE6RHohS.js, line 45

Somehow, and I don't know why, autostart is true when QUnit starts up when the app uses a top level await, a component like this can recreate the issue.

import Component from '@glimmer/component';
const sleep = (ms: number) => new Promise((resolve) => setTimeout(resolve, ms));
await sleep(1000);

export default class MyComponent extends Component {}

I found this by using dynamic import at the top level to make a large library it's own chunk. I think it's down to bundle ordering, but I'm not sure.

Using qunit's preconfig option ensures autostart is false and top level awaits don't break the test suite.

More context on discord
https://discord.com/channels/480462759797063690/568935504288940056/1319396012506484850
https://discord.com/channels/480462759797063690/568935504288940056/1320540566274179182
https://discord.com/channels/480462759797063690/568935504288940056/1321109960117063773