[ty] highlight special type syntax in hovers as xml (#22005)
## Summary
These types look better rendered as XML than python
## Test Plan
<img width="532" height="299" alt="Screenshot 2025-12-16 at 8 40 56 AM"
src="https://github.com/user-attachments/assets/42d9abfa-3f4a-44ba-b6b4-6700ab06832d"
/>
