[ROCm][CI] Add rocm support for run-multi-node-test.sh

[charlifu]

Now run-multi-node-test.sh only works for cuda, this PR add support for rocm by:

• check if on rocm or not
• using different flags for rocm to control gpu devices used inside ci image.

[gemini-code-assist]

Code Review

This pull request adds support for ROCm to the multi-node test script. The changes include logic to detect a ROCm environment and to use the appropriate Docker flags for either ROCm or CUDA. The overall approach is sound, but I've found a critical syntax error in the shell script that will cause it to fail. Please see the specific comment for details.

[tjtanaa]

LGTM

[tjtanaa]

@charlifu we will also need to update the ci-infra repo as this bash script is not called at all. Everything is run by run-amd-test.sh right now.

https://buildkite.com/vllm/amd-ci/builds/2429/steps/canvas?sid=019b9440-620f-4e65-9204-d1f4b5939080

For CUDA they have this render_cuda_config that triggers tests with num_nodes >= 2 to be run by run-multi-node-test.sh
https://github.com/vllm-project/ci-infra/blob/46c6cc39549c3cbecc827983bf002a1ed23d426c/buildkite/test-template-ci.j2#L52

For AMD CI test template, but this render_cuda_config macro is never used
https://github.com/vllm-project/ci-infra/blob/46c6cc39549c3cbecc827983bf002a1ed23d426c/buildkite/test-template-amd.j2#L97

CC @AndreasKaratzas