Fixed 30s timestamp resets in Whisper long-form transcription

[FaresBadrCA]

What does this PR do?

Fixes #34210 and #31942.
This is an alternative to PR #35750

It resolves the issue of timestamps rolling over every 30 seconds in the Whisper model's long-form transcription. It does this by forcing return_segments to be True when return_timestamps is True.

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Who can review?

@eustlb, @Rocketknight1, @gante, @ylacombe

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