[Feature]: Remove cupy dependency for multi-node Ray deployment

[stephanie-wang]

🚀 The feature, motivation and pitch

Ray uses cupy under the hood for inter-GPU communication in compiled graphs. We should remove the dependency by creating the collective group using existing vllm APIs and providing a handle to the group to Ray.

Alternatives

• Ray could use provide its own NCCL bindings - note this would not support non-NVIDIA GPUs

Additional context

No response

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[youkaichao]

Ray could use provide its own NCCL bindings - note this would not support non-NVIDIA GPUs

it actually works for amd rocm gpus too, just need to change the shared library name. the binding interface is the same.