[veomni, vllm] feat: Allow gptoss ep with veomni - #7397

What does this PR do?

Enable gpt-oss RL training with veomni EP for gpt-oss family model. In conjuncture with this vllm PR:
vllm-project/vllm#52209

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Test

Performed e2e testing with veomni (ep = 8) + vllm (ep = 8):

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