[AMD] Qwen3.5-FP8 MI355X SGLang disagg perf tuning: image bump to v0.5.16, TP4P+TP8D baseline, add MTP / Qwen3.5-FP8 MI355X SGLang disagg 性能调优：镜像升级至v0.5.16，TP4P+TP8D基线优化，新增MTP配置 - #2557