Update project version to : `3.1.8-SNAPSHOT` #5589

Job	Run time
Run examples in 'session-example' on MySQL	2m 5s
Test with MariaDB	4m 6s
Run examples in 'session-example' on PostgreSQL	2m 16s
Run examples in 'native-sql-example' on PostgreSQL	2m 10s
Test with MySQL	4m 34s
Test with MSSQLServer	4m 49s
Test with CockroachDB	5m 53s
Test with PostgreSQL	4m 28s
Test with Java 25	3m 54s
Test with Java 21	3m 52s
Test with Db2	5m 55s
Test with Java 20	3m 20s
Test with Oracle	5m 38s
Test with Java 24	3m 37s
Test with Java 26-ea	3m 38s
Test with Java 17	3m 35s
	1h 3m 50s

Provide feedback