Remove JUnit 4 dependency from all modules except spring-test

This commit removes the JUnit 4 dependency from all modules except
spring-test which provides explicit JUnit 4 support.

This commit also includes the following.

- migration from JUnit 4 assertions to JUnit Jupiter assertions in all
  Kotlin tests
- migration from JUnit 4 assumptions in Spring's TestGroup support to
  JUnit Jupiter assumptions, based on org.opentest4j.TestAbortedException
- introduction of a new TestGroups utility class than can be used from
  existing JUnit 4 tests in the spring-test module in order to perform
  assumptions using JUnit 4's Assume class

See gh-23451

spring-beans/src/test/java/org/springframework/beans/factory/serviceloader/ServiceLoaderTests.java

@@ -26,7 +26,7 @@ import org.springframework.beans.factory.support.DefaultListableBeanFactory;
 import org.springframework.beans.factory.support.RootBeanDefinition;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.junit.Assume.assumeTrue;
+import static org.junit.jupiter.api.Assumptions.assumeTrue;
 
 /**
  * @author Juergen Hoeller