[beelapranay]

What does this PR do?

Refactors FNet and CVT output tracing to use the standardized decorators where appropriate.

1. FNet now uses @capture_outputs with _can_record_outputs to collect hidden states.
2. CVT keeps manual hidden-state collection to preserve vision-model semantics.
3. Wrapper heads use @can_return_tuple to simplify return_dict handling.

Fixes #43979

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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• Did you write any new necessary tests?

Who can review?

@molbap @ArthurZucker

[github-actions]

[For maintainers] Suggested jobs to run (before merge)

run-slow: cvt, fnet

[ArthurZucker]

Thanks for the refactor, @beelapranay! The #43979 call to contributions was closed shortly after this was opened and we couldn't review the many PRs it produced, so I'm closing this one. Sorry it didn't get looked at in time.