Rename test fixture package in spring-core

See gh-23550

spring-orm/src/test/java/org/springframework/orm/jpa/AbstractContainerEntityManagerFactoryIntegrationTests.java

@@ -26,7 +26,7 @@ import javax.persistence.Query;
 
 import org.junit.jupiter.api.Test;
 
-import org.springframework.core.test.fixtures.io.SerializationTestUtils;
+import org.springframework.core.testfixture.io.SerializationTestUtils;
 import org.springframework.orm.jpa.domain.DriversLicense;
 import org.springframework.orm.jpa.domain.Person;
 

spring-orm/src/test/java/org/springframework/orm/jpa/LocalContainerEntityManagerFactoryBeanTests.java

@@ -32,7 +32,7 @@ import javax.persistence.spi.ProviderUtil;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.beans.factory.support.DefaultListableBeanFactory;
-import org.springframework.core.test.fixtures.io.SerializationTestUtils;
+import org.springframework.core.testfixture.io.SerializationTestUtils;
 import org.springframework.dao.DataAccessException;
 import org.springframework.dao.OptimisticLockingFailureException;
 import org.springframework.instrument.classloading.InstrumentationLoadTimeWeaver;

spring-orm/src/test/java/org/springframework/orm/jpa/support/PersistenceInjectionTests.java

@@ -39,7 +39,7 @@ import org.springframework.beans.factory.support.RootBeanDefinition;
 import org.springframework.context.support.GenericApplicationContext;
 import org.springframework.context.test.fixtures.SimpleMapScope;
 import org.springframework.context.test.fixtures.jndi.ExpectedLookupTemplate;
-import org.springframework.core.test.fixtures.io.SerializationTestUtils;
+import org.springframework.core.testfixture.io.SerializationTestUtils;
 import org.springframework.lang.Nullable;
 import org.springframework.orm.jpa.AbstractEntityManagerFactoryBeanTests;
 import org.springframework.orm.jpa.DefaultJpaDialect;