Turbopack: fix filesystem watcher config not applying follow_symlinks(false) (#92631)
## Summary
- The notify `Config` uses a builder pattern where `with_follow_symlinks()` consumes `self` and returns a new `Config`, but the return value was being discarded — so `follow_symlinks` remained at its default (`true`).
- The `RecommendedWatcher` branch was also passing `Config::default()` instead of the configured `config` object, ignoring the config entirely.
## Test plan
- [x] `cargo check -p turbo-tasks-fs` passes
- Behavioral: symlinks under the watched root will now trigger events for the symlink itself rather than the target, matching the intent of the existing comment.
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