Do not idle in the event loop if there are pending immediate tasks

[190n]

What does this PR do?

Fixes #17725. The presence of a setInterval timer would make us idle in us_loop_run_bun_tick on every run of the event loop for a dozen ms or so, but that's not a good idea when we have immediate tasks to run. This PR makes us skip the timeout if there are immediate tasks, similar to what we already do if there is a short timer (in terms of the effect on idling, immediates are like 0ms timers).

Todo:

• see how much we can benefit JSZip
• fix Windows failure

How did you verify your code works?

Ran the node:timers tests, and extended our own tests to cover a use case like #17725.

[robobun]

^{Updated 9:23 PM PT - Mar 6th, 2025}

❌ @190n, your commit 6005944 has 2 failures in Build #12808:

• test/js/bun/shell/leak.test.ts - timeout on 🍎 13 aarch64
• test/cli/install/bun-install-registry.test.ts - 1 failing on 🪟 2019 x64

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🧪   try this PR locally:

bunx bun-pr 17901

[dylan-conway]

Is it possible this fixes #11054?

[190n]

It might, I need to test that.