[Turbopack] Transient Tasks (#68436)
### What?
use different task ids for persistent and transient tasks
Store transient tasks separately Rename PersistentTaskType ->
CachedTaskType
Track which tasks are transient and which are persistent.
### Why?
We need to track that for persistent caching.
We use a different task id space for transient tasks so they don't use
up persistent ids and to easily identify transient tasks.
### How?
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Co-authored-by: Benjamin Woodruff <benjamin.woodruff@vercel.com>
