[Feature] Multi-node Ray support for GRPO sota-implementation

[albertbou92]

Description

This PR extends the GRPO sota-implementation and adds support for multi-node settings:

• run_in_ray_cluster.sh: wraps any command with Ray head/worker setup
• grpo-sync-multi-node.sbatch and grpo-async-multi-node.sbatch: SLURM scripts to launch multi-node GRPO training

Useful for scaling out GRPO experiments on cluster environments.

Motivation and Context

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[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/rl/3040

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