Make classes final where possible

Update classes that have private constructors so that they are also
declared final. In a few cases, inner-classes used private constructors
but were subclassed. These have now been changed to have package-private
constructors.

Issue gh-8945

core/src/test/java/org/springframework/security/PopulatedDatabase.java

@@ -26,7 +26,7 @@ import org.springframework.jdbc.core.JdbcTemplate;
  *
  * @author Ben Alex
  */
-public class PopulatedDatabase {
+public final class PopulatedDatabase {
 
 	private static TestDataSource dataSource = null;