Turbopack: Scope with work queue (#84225)
### What?
* Use a work queue and worker tasks in the scope implementation to reduce the number of spawned tokio tasks. Only spawn a tokio task per CPU - 1.
* Run work in the current tokio task too to avoid blocking time and use one less task.
Before we only did a blocking wait on the current tokio task, which did require calling block_in_place pretty often.
Now we also do work on the current tokio task too, which requires calling block_in_place less often. (We only call block_in_place when we need to block longer than 1ms)
