[Kernel] Enable custom AR on ROCm

[wenkaidu]

This patch enables custom all reduce on AMD GPUs which are connected via 1-hop XGMI. It allocates special "uncached" memeory for signal buffers which are necessary on MI100/MI200 GPUs.

XGMI link information is queried via amdsmi py-interface: https://github.com/ROCm/amdsmi/blob/develop/py-interface/README.md

To install amdsmi:
cd /opt/rocm/share/amd_smi/
pip install .

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FIX #xxxx (link existing issues this PR will resolve)

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[mawong-amd]

I've stress-tested the changes extensively for correctness. Haven't run into any issues so far. I can also confirm an end-to-end latency improvement of up to 8% for a large variety of workloads.

Thank you @wenkaidu for taking the time to enable this correctly on ROCm for many platforms—painstaking work that has led to an obvious improvement in performance!