Replace unnamed tuple in cls result with a label object

[sovrasov]

What does this PR do?

Tuple-like behavior is preserved to avoid client code changes:

predictions: ClassificationResult

for label_idx, label_name, prob in predictions.top_labels:
    ...

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you make sure to update the documentation with your changes?
• Did you write any new necessary tests?