[rollout] feat: add enable_sleep_mode=false update to use expandable_segments when in RolloutMode.STANDALONE

[chenjiaoAngel]

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add enable_sleep_mode=false update to use expandable_segments when in RolloutMode.STANDALONE

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[gemini-code-assist]

Code Review

This pull request updates the vLLM async server to disable sleep mode and enable expandable segments when running in STANDALONE mode. The logic correctly modifies the enable_sleep_mode argument for the vLLM engine. However, there is a critical issue where the set_expandable_segments function is called without being imported, which will cause a runtime error. This needs to be fixed by adding the appropriate import statement.