A lighter InsertPlan for single data point insertion scenario

It is very common to insert data point by point into a single time series. For this scenario, IoTDB's InsertPlan is very unfriendly: a large number of array objects need to be constructed.

I suggest adding a separate InsertPlan (and corresponding execution logic) for this scenario to improve performance.


该 issue 涉及 IoTDB 的 InsertPlan，用于向单个时间序列一次插入一个数据点。首先跟踪当前 InsertPlan 的构造及其执行逻辑，然后将提议的路径与现有路径进行比较。当存在一条独立且更轻量的插入路径，能够减少数组对象的构造并提升此场景下的性能时，即视为完成。

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