Support DSV4 Flash

**Is your feature request related to a problem? Please describe.**
Support RL training for DSV4 Flash.
Automodel dependency: https://github.com/NVIDIA-NeMo/Automodel/issues/2034
vLLM dependency: https://github.com/vllm-project/vllm/pull/40760

**Describe the solution you'd like**
A clear and concise description of what you want to happen.

**Describe alternatives you've considered**
A clear and concise description of any alternative solutions or features you've considered.

**Additional context**
related watch list https://github.com/zpqiu/NeMo-RL/issues/8