[vllm] Implement int8 rollout using the flash_rl tool on NPU

[nuerxiati]

What does this PR do?

On Ascend device using the Flash-RL tool to modify the inference backend and perform online quantization of weights and activation values ​​by comparing INT8 and BF16 models. Uses the Qwen3-30B INT8 as an example to demonstrate how to run the end-to-end functionality on the NPU.

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Test

Throughput bf16: 167, int8: 195, increased by 16.8%; reward bf16: -0.1012, int8: -0.1204, decreased by 0.96%;

Precision：

Performence：

int8 100steps rewards:

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