Define a constant instead of duplicating this literal "total" 8 times.

Code Path:confignode/src/main/java/org/apache/iotdb/confignode/manager/load/LoadManagerMetrics.java

Duplicated string literals make the process of refactoring error-prone, since you must be sure to update all occurrences.
On the other hand, constants can be referenced from many places, but only need to be updated in a single place.

打开 confignode/src/main/java/org/apache/iotdb/confignode/manager/load/LoadManagerMetrics.java，找到重复的八个 "total" 字面量。定义一个常量并将其用于这些引用；当该字面量不再在那里重复且现有行为保持不变时，即表示完成。

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