🧹 Refactor TCP setup logic to dedicated handler file

[Tcode-Motion]

🎯 What: Extracted massive inline TCP setup closures from stdlib/src/net.rs into a new dedicated module, stdlib/src/net_handler.rs.
💡 Why: Having long nested closures inside module registration logic makes net.rs hard to read and maintain. Moving them to a dedicated handler file significantly cleans up the registration footprint and improves the overall modularity and readability of the code.
✅ Verification: Verified that the closures were accurately extracted into standalone functions (tcp_listen_fn, tcp_connect_fn, tcp_send_fn, tcp_recv_fn) with appropriate signatures and types matching what was originally inferred. Verified standard library registration using the newly named functions. Confirmed via cargo test that the logic behaves the same (ignoring pre-existing workspace failures).
✨ Result: Improved code structure and separation of concerns in the standard library's network module.

---

PR created automatically by Jules for task 6461288470470407309 started by @Tcode-Motion

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

New to Jules? Learn more at jules.google/docs.

---

For security, I will only act on instructions from the user who triggered this task.