Followup of #27026

For setTimeout triggered by string code, we currently failed at finding its correct execution context so it will fetch a wrong link.

Corresponding spec link: https://html.spec.whatwg.org/multipage/#timer-initialisation-steps

I haven't digged into it but I think we need to pass base url of the timer and we might need to save it in JsTimerTask.

I wonder if it's good to be a follow-up issue, if not, I can try to fix it in this PR!

(Interestingly, only Firefox executes correctly on all the setTimeout tests for dynamic import module 😂)

Originally posted by @CYBAI in #27026