Use setTimeout for async work

[nikku]

Proposed Changes

Requests to requestAnimationFrame may be dropped, depending on how the browser feels. This is what makes tests under Ubuntu/Firefox fail, but it may also cause issues in other high stress scenarios.

If we want to reliably ensure work gets done, we have to setTimeout(work) things. This is what I propose in 8f33e8b.

Closes #921

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[nikku]

This can be reproduced somewhat locally using the Firefox headless runner, but only when running the whole test suite. Executing only the scheduler specs passes.

Current assumption is that we don't properly cleanup the scheduler, or that Firefox swallows the requestAnimationFrame calls (likely).

[nikku]

As suspected this is about Firefox dropping frames under high load (aka huge page) setups.

In order to reliably do stuff we have to await or setTimeout (can be canceled) it, cf. 8f33e8b.

[nikku]

Executing test on Firefox takes whooping 12 minutes:

[barmac]

Hmm maybe we should not rush it. This causes some tests to fail on my machine (MacOS, Chrome Headless 129).

[barmac]

I'll check on fresh install.

[barmac]

OK so I guess I am now suffering from the same problem as Firefox before the changes. On main, I can npm run all all green, but with this PR, the tests start to timeout :/

[barmac]

And the tests are very old, rather unrelated to scheduler.