[AMD] perf: enable FlyDSL w4a16 MoE for Kimi INT4

[amd-asalykov]

Replace default triton w4a16 MoE kernel with more performant FlyDSL implementation for Kimi INT4 MI355X

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Note

Low Risk
Benchmark and serving-flag changes only; no application auth or data paths. Risk is limited to reproducibility and CI cost from expanded sweeps and a nightly container pin.

Overview
Updates the Kimi K2.5 INT4 vLLM MI355X benchmark to use FlyDSL for w4a16 MoE instead of the default Triton path, and pins a digest-suffixed ROCm nightly image (vllm-openai-rocm:nightly-b8336c3…).

The runner script kimik2.5_int4_mi355x.sh adds --moe-backend flydsl and a compilation pass that sets fuse_allreduce_rms to false. CI config expands the fixed-seq-len sweep: concurrency up to 128 (from 64) and an additional TP=4 row for both 1k/1k and 8k/1k scenarios.

perf-changelog.yaml records the config-key change for PR #1777.

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