[vllm] fix: pad data_hp to be multiples of block_size

[Agoniii]

What does this PR do?

To fix the issue: #4822

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[gemini-code-assist]

Code Review

This pull request correctly addresses a potential crash in scaled_fp8_blockwise by replacing a strict assertion with a padding mechanism. The code now pads input tensors to ensure their dimensions are multiples of the block size, which is necessary for blockwise FP8 quantization. The implementation is clean, saving the original shape and cropping the tensor back after processing.

A significant concern is that an almost identical function, also named scaled_fp8_blockwise, exists in verl/utils/sglang/sglang_fp8_utils.py. This function has not been updated and still contains the original assertion, which will lead to the same crash if used. To prevent this bug and improve maintainability by reducing code duplication, it is highly recommended to apply the same padding logic to the sglang utility file. This could be done in this PR or a follow-up.