[IOTDB-6236] Pipe: CountPointProcessor example

[yschengzi]

Simple PipeProcessor plugin:
Main function: In standalone case, it can count the total number of IoTDB points in real time and write them into a target sequence (specified by the KV parameter of the Processor).

简易 PipeProcessor 插件：
主要功能：单机情况下，可以实时统计 IoTDB 的总点数并写成目标序列（由 Processor 的 KV 参数指定）

使用方法：

IoTDB: create pipeplugin c as 'org.apache.iotdb.CountPointProcessor' using URI 'file:///local/count-point-processor-example-1.3.0-SNAPSHOT.jar'
IoTDB: create pipe p with processor( 'processor' = 'c', 'aggregate-series'='root.sg.res.count', ) with connector ( 'connector'='iotdb-thrift-connector', 'connector.ip'='127.0.0.1', 'connector.port'='6668',)