Enable CPU nightly performance benchmark and its Markdown report

[louie-tsai]

Need to standardize vLLM CPU benchmarks among customers and intel users by using vLLM benchmark suite.
Also hope to enable CPU perf numbers on vLLM performance dashboard.

Enable vLLM benchmark suite for CPU and below are snapshot of serving benchmark report.
numbers are aligned with our Xeon EMR numbers.

How to run it on CPU under vllm folder:
ON_CPU=1 bash .buildkite/nightly-benchmarks/scripts/run-performance-benchmarks.sh

also added a new section "Platform Information" section to list out CPU info

Here is the full report.
benchmark_results_0527_3.md

overall, it took ~2 hours for current tests.

it also needs to have auto OMP thread binding from below PR.
#17930

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[louie-tsai]

@bigPYJ1151 could you help to review this PR?