Skip os.makedirs for GCS profile paths in TPU worker

[subhamsoni-google]

The C++ profiler backend (tsl::Env) natively supports gs:// paths via RetryingGcsFileSystem, handling directory creation internally. Guard the os.makedirs call to only run for local filesystem paths, preventing it from creating a spurious local directory named "gs:/bucket/..." when a GCS URI is passed as torch_profiler_dir.

Add tests verifying:

• GCS paths skip os.makedirs on rank 0 (single PP)
• GCS paths skip os.makedirs in pipeline-parallel mode
• Local paths still call os.makedirs in pipeline-parallel mode
• GCS paths are passed directly to jax.profiler.start_trace

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[subhamsoni-google]

I have verified over GKE env, that the vllm via the logdir is working perfectly fine.