Remove testsuite use of org.hibernate.stat.Statistics.getSecondLevelCacheStatistics

org,hibernate.stat.Statistics.getSecondLevelCacheStatistics() is deprecated in 5.3 in favor of getDomainDataRegionStatistics(). The method is removed in Hibernate 6 so switch testsuite use to getDomainDataRegionStatistics() to ease the migration to Hibernate 6.