Deprecate Junit 4 helpers?

These helpers

• BaseContextMockTest
• BaseContextSensitiveTest
• BaseModuleContextSensitiveTest
• BaseModuleWebContextSensitiveTest

that are based on JUnit 4 need to be deprecated so module developers are aware that they should at some point migrate to JUnit 5.

{{public abstract class BaseContextSensitiveTest extends AbstractJUnit4SpringContextTests { }}
BaseContextMockTest is pre Junit 5 Extensions

Also make sure all the new helpers have updated javadocs that mention that they are for JUnit 5 tests. The javadocs should also contain a @since annotation.

We have to think about how long we want to support JUnit 4 tests in openmrs-core/test so we can one day remove these helpers and the JUnit 4 dependencies.