refactor(turbo-tasks): Split local and global task state (#68963)
With tasks that use `local_cells`, they'll need to inherit some
information from their parent non-local task (e.g. the `task_id`, cell
counters, etc), but not everything is inherited (e.g. the function
metadata).
Splitting `CURRENT_TASK_STATE` into two separate task locals allows us
to modify this inherit-some-but-not-all behavior.
**Sidenote:** `CURRENT_LOCAL_TASK_STATE` is never mutated, so it doesn't
need a `RefCell` or `RwLock` wrapper.
## Testing
Should be identical in functionality.
```
cargo nextest r -p turbo-tasks-memory -p turbo-tasks --no-fail-fast
```