### What this PR does / why we need it?
Support an new load format: RFORK
For implementation details of this feature, please refer to #7441
### Does this PR introduce _any_ user-facing change?
add an new options for load-format: rfork
e.g.
```bash
vllm serve /workspace/models/Qwen3-8B --load-format rfork
```
### How was this patch tested?
- vLLM version: v0.17.0
- vLLM main:
4034c3d32e
Signed-off-by: Marck <1412354149@qq.com>