Enable granite 4 hybrid integration tests
Author: alex-jw-brooks
Pull request: yes

Enables granite moe hybrid integration tests using the tiny preview model. Tolerance is adjusted to be more lenient for bfloat16.

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Fixes # https://github.com/huggingface/transformers/issues/38542


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@ydshieh can you please take a look?

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

run-slow: granitemoehybrid

Thank you a lot. I will check the tests in our runner.

@alex-jw-brooks 

Do you know why `test_model_logits` have different `out.logits.float().mean(-1)` in different runs?

It's just forward and should give deterministic outputs no?

@ydshieh I agree, but this doesn't seem to be the case, and it seems to diverge a lot more when it's run with bf16. Please let me investigate a bit - I'll follow up once I at least have a better understanding of the root cause of the non-determinism 🙂 

It's known bf16 have less precision (to have wilder range). I'm happy to change it to fp32 (if it fits into A10).
The worrying part is more about the non-deterministic outputs in different runs.

That would be nice if we can figure out why?

(Maybe first check if all model's weights are loaded from the model checkpoint - if not we will see some warning from the log. But I think it is correctly loaded otherwise the output would be even non-sense).

Thank you for helping 🙏 

Unfortunately, it won't without CPU offload, it's about 30 gb of vram to run it in full precision 😞 This model is pretty much combining elements from bamba and granite moe shared - I'm guessing it's something to do with bamba and hopefully expected since the [bamba integration tests](https://github.com/huggingface/transformers/blob/main/tests/models/bamba/test_modeling_bamba.py#L593) use similarly high tolerance for these checks, but just need to dig a bit to understand since I'm less familiar with SSMs in general 😅 

I'll follow up as soon as possible, and also see if anything can be done about getting a smaller model for testing!