[Bugfix][CI][V1] Work around V1 + CUDA Graph + torch._scaled_mm fallback issue

[tlrmchlsmth]

This PR works around an issue where vLLM V1, using Ada Lovelace GPUs, and when building vLLM with CUDA < 12.4, FP8 models with per-channel and/or per-tensor quantization will produce garbage output.

Closes #13212

AFAICT, there is some issue with the way we are setting up TORCH_DEVICE_IDENTITY

Alternatively, now that torch._scaled_mm supports rowwise scaling we could use that instead of the fallback. Unfortunately this only works if the model's dtype is bf16. Otherwise we get the error:

RuntimeError: Only bf16 high precsion output types are supported for row-wise scaling.

Definitely am not happy about the approach here as is puts the onus on the caller of apply_fp8_linear to also call maybe_create_device_identity before the forward pass.

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[mgoin]

Certainly agree it is unfortunate, but this is critical to fix now. Nice work and LGTM