feat: add seed offset args to sampler to allow cuda graph support (#2132)

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## 📌 Description

This PR adds optional seed/offset args to all the sampler functions to
prevent calling the `get_seed_and_offset` function. If that function is
not called, we can potentially make the sampler forward call as part of
CUDAGraph and use that to replay it.

We can directly compute the Seed/offset values, before launching the
graph in a similar way to as it is being done in the current method and
pass them when making the flashinfer call

## 🔍 Related Issues
#978 : top_k_top_p_sampling_from_logits incompatible with torch.compile
+ CUDAGraph

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## 🧪 Tests

- [x] Tests have been added or updated as needed.
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<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit

* **New Features**
* Optional seed and offset parameters added to sampling APIs to enable
deterministic RNG control while remaining optional.

* **Tests**
* New tests verify reproducible sampling when using the same seed/offset
and variability when different values are used.

<sub>✏️ Tip: You can customize this high-level summary in your review
settings.</sub>
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: ksukrit