[ROCm][perf] Shuffle KV cache to use paged_attention_common

[samutamm]

Purpose

For Qwen/Qwen3-235B-A22B-Instruct-2507-FP8 model, currently VLLM_ROCM_SHUFFLE_KV_CACHE_LAYOUT=1 performs worse on small concurrencies, compared to VLLM_ROCM_SHUFFLE_KV_CACHE_LAYOUT=0. This PR fixes the issue using paged_attention_common from aiter (see ROCm/aiter#1821).

Test Plan

For input and output lengths of 1k and 8k and concurrencies from 8, 18, 32, 64, 128, compare current main branch with and without VLLM_ROCM_SHUFFLE_KV_CACHE_LAYOUT (_vllm_main_shuffle1 and _vllm_main_shuffle0, respectively) to changes of this PR (_pr_shuffle1).

Also verified on MI355.
Also verified for Qwen/Qwen3-235B-A22B-Instruct-2507.

Test Result

For input length 8k and output length 1k (green lines), the changes of this PR (_pr_shuffle1, the solid line) outperform main branch, with or without shuffle kv cache.
For input length 1k and output length 8k (orange lines), the changes of this PR (_pr_shuffle1, the solid line) outperform main branch, with or without shuffle kv cache.
For input length 1k and output length 1k (blue lines), the changes of this PR (_pr_shuffle1, the solid line) are very close to main branch. This might require further adjustment in aiter paged_attention_common.

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