Move spring-build-junit into spring-core

Move code from spring-build-junit into spring-core/src/test along with
several other test utility classes. This commit removes the temporary
spring-build-junit project introduced in commit
b083bbdec7.

src/test/java/org/springframework/scheduling/annotation/ScheduledAndTransactionalAnnotationIntegrationTests.java

@@ -23,14 +23,14 @@ import org.junit.Test;
 
 import org.springframework.aop.support.AopUtils;
 import org.springframework.beans.factory.BeanCreationException;
-import org.springframework.build.junit.Assume;
-import org.springframework.build.junit.TestGroup;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor;
 import org.springframework.dao.support.PersistenceExceptionTranslator;
 import org.springframework.stereotype.Repository;
+import org.springframework.tests.Assume;
+import org.springframework.tests.TestGroup;
 import org.springframework.transaction.CallCountingTransactionManager;
 import org.springframework.transaction.PlatformTransactionManager;
 import org.springframework.transaction.annotation.EnableTransactionManagement;