Turbopack: lazy require metadata and handle TLA (#91705)
A regression from #88487
1. Make metadata import lazy with `() => require()`, just like for the layout segments
2. Properly await the return value to better handle TLA modules
This align with Webpack which does this:
<img width="1535" height="509" alt="Bildschirmfoto 2026-03-20 um 11 58 00" src="https://github.com/user-attachments/assets/f2864c86-ccce-4884-8417-c8ae06c05f78" />
Closes PACK-6927
Closes #91700
Closes https://github.com/vercel/next.js/issues/91676
