GumKey

https://github.com/apache/seatunnel/blob/dev/seatunnel-connectors-v2/connector-cdc/connector-cdc-base/src/main/java/org/apache/seatunnel/connectors/cdc/base/source/enumerator/splitter/AbstractJdbcSourceChunkSplitter.java The split column selection order is： 1、primary key and primary key type is tinyint 2、unique key and unique key type is tinyint 3、no tinyint key , compare primary key...

> Please add test case. Test case have been added, take a look.