[rollout] feat: Support Multi-stage Awake for SGLang+Megatron

[SuperCB]

What does this PR do?

PR (https://github.com/volcengine/verl/pull/1911) did not include Multi-stage Awake for Megatron+Sglang. This PR implemented that functionality. After this feature is completed, the sglang's mem_fraction_static parameter can be set to 0.9 or even higher.

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[hebiao064]

Please wait for this PR: #2187