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
979508a7f3