[Flight] Add a cached 3rd-party component to the Flight fixture (#33443)

This should allow us to visualize what
https://github.com/facebook/react/pull/33438 is trying to convey.

An uncached 3rd-party component is displayed like this in the dev tools:

<img width="1072" alt="Screenshot 2025-06-05 at 12 57 32"
src="https://github.com/user-attachments/assets/d418ae23-d113-4dc9-98b8-ab426710454a"
/>

However, when the component is restored from a cache, it looks like
this:

<img width="1072" alt="Screenshot 2025-06-05 at 12 56 56"
src="https://github.com/user-attachments/assets/a0e34379-d8c0-4b14-8b54-b5c06211232b"
/>

The `Server Components ⚛` track is missing completely here, and the
`Loading profile...` phase also took way longer than without caching the
3rd-party component.

On `main`, the `Server Components ⚛` track is not missing:

<img width="1072" alt="Screenshot 2025-06-05 at 14 31 20"
src="https://github.com/user-attachments/assets/c35e405d-27ca-4b04-a34c-03bd959a7687"
/>

The cached 3rd-party component starts before the current render, and is
also not excluded here, which is of course expected without #33438.