[Nightly] Dump logs file from kubernetes

[Potabk]

What this PR does / why we need it?

Does this PR introduce any user-facing change?

How was this patch tested?

• vLLM version: v0.11.2
• vLLM main: https://github.com/vllm-project/vllm/commit/v0.11.2

[github-actions]

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[gemini-code-assist]

Code Review

This pull request introduces several improvements to the nightly multi-node testing infrastructure, focusing on logging and robustness. Key changes include adding a timeout to the ranktable generation, refactoring the server health-check logic in conftest.py to be more resilient and provide better diagnostics, and overhauling the run.sh script for better log management and failure analysis. These are valuable enhancements for test reliability. However, I've identified critical security vulnerabilities in the run.sh script related to unsafe directory removal commands, which could lead to unintended file deletions. These issues must be addressed.