chore: drop the legacy single-node gpu_metrics.csv power consumer

main removed it in #3675 together with the client-side GPU monitor that fed it; the #3684 merge brought it back with no caller.

中文：删除旧版单节点 gpu_metrics.csv 功耗消费代码；主干已在 #3675 连同喂给它的客户端 GPU 监控一起移除，#3684 合并时被带回且无任何调用方。

Author: edwingao28