[COST] Provide descriptive Object#toString for ClusterCosts

[garyparrot]

Context: #1463 (comment)

這個 PR 給 ClusterCost 提供 Object#toString() 實作，該實作將會暴露關於自己分數的一些細部統計資訊。給使用者一些提示這個數字背後的故事。預期套用這個 PR 後， ClusterCost 分數背後的來源會比較透明一些。

• 修改 ClusterCost，現在一定要透過 ClusterCost#of(double) 或 ClusterCost#of(double,Supplier<String>) 函數來建立。
• ClusterCost#of(double, Supplier<String>) 簽名提供一個參數來指出這個 ClusterCost 的細部資訊（以字串顯示），這個字串內容會在 HasClusterCost#of() 回傳的版本中出現。
• 給每個 HasClusterCost 的實作添加適合的 ClusterCost 敘述字串

範例

    var clusterCost =
        HasClusterCost.of(
            Map.of(
                new ReplicaNumberCost(), 1D,
                new NetworkIngressCost(), 10D,
                new NetworkEgressCost(), 10D));
    // ...
    var plan = balancer.offer(clusterInfo, Duration.ofSeconds(10));
    System.out.println(plan.initialClusterCost());
    System.out.println(plan.solution().get().proposalClusterCost());

輸出

WeightCompositeClusterCost[{"NetworkEgressCost" cost 0.3656846459646673 weight 10.0 description {2.02 GB/seconds, 1.95 GB/seconds, 3.07 GB/seconds} }, {"NetworkIngressCost" cost 0.24225888389074973 weight 10.0 description {2.02 GB/seconds, 1.95 GB/seconds, 2.57 GB/seconds} }, {"ReplicaNumberCost" cost 0.001998001998001998 weight 1.0 description LongSummaryStatistics{count=3, sum=1001, min=333, average=333.666667, max=335} }] = 0.28959206193105586
WeightCompositeClusterCost[{"NetworkEgressCost" cost 0.18654063812123348 weight 10.0 description {2.18 GB/seconds, 2.18 GB/seconds, 2.68 GB/seconds} }, {"NetworkIngressCost" cost 1.3078499909827186E-4 weight 10.0 description {2.18 GB/seconds, 2.18 GB/seconds, 2.18 GB/seconds} }, {"ReplicaNumberCost" cost 0.08191808191808192 weight 1.0 description LongSummaryStatistics{count=3, sum=1001, min=283, average=333.666667, max=365} }] = 0.09279201491054283

手動換行後的輸出

WeightCompositeClusterCost[
  {"NetworkEgressCost" cost 0.3656846459646673 weight 10.0 description {2.02 GB/seconds, 1.95 GB/seconds, 3.07 GB/seconds} },
  {"NetworkIngressCost" cost 0.24225888389074973 weight 10.0 description {2.02 GB/seconds, 1.95 GB/seconds, 2.57 GB/seconds} },
  {"ReplicaNumberCost" cost 0.001998001998001998 weight 1.0 description LongSummaryStatistics{count=3, sum=1001, min=333, average=333.666667, max=335} }
] = 0.28959206193105586
WeightCompositeClusterCost[
  {"NetworkEgressCost" cost 0.18654063812123348 weight 10.0 description {2.18 GB/seconds, 2.18 GB/seconds, 2.68 GB/seconds} }, 
  {"NetworkIngressCost" cost 1.3078499909827186E-4 weight 10.0 description {2.18 GB/seconds, 2.18 GB/seconds, 2.18 GB/seconds} }, 
  {"ReplicaNumberCost" cost 0.08191808191808192 weight 1.0 description LongSummaryStatistics{count=3, sum=1001, min=283, average=333.666667, max=365} }
] = 0.09279201491054283

[chia7712]

LGTM