junit: Make internal classes package-private

This removes the classes from generated javadocs.

Author: fmeum

src/main/java/com/code_intelligence/jazzer/junit/AgentConfiguringArgumentsProvider.java

@@ -22,8 +22,7 @@
 import org.junit.jupiter.params.provider.ArgumentsProvider;
 import org.junit.jupiter.params.support.AnnotationConsumer;
 
-public class AgentConfiguringArgumentsProvider
-    implements ArgumentsProvider, AnnotationConsumer<FuzzTest> {
+class AgentConfiguringArgumentsProvider implements ArgumentsProvider, AnnotationConsumer<FuzzTest> {
   private FuzzTest fuzzTest;
 
   @Override

src/main/java/com/code_intelligence/jazzer/junit/JUnitLifecycleMethodsInvoker.java

@@ -37,7 +37,7 @@
  * Adapts JUnit BeforeEach and AfterEach callbacks to {@link
  * com.code_intelligence.jazzer.driver.FuzzTargetRunner} lifecycle hooks.
  */
-public class JUnitLifecycleMethodsInvoker implements LifecycleMethodsInvoker {
+class JUnitLifecycleMethodsInvoker implements LifecycleMethodsInvoker {
   private final ThrowingRunnable[] beforeEachExecutionRunnables;
 
   private long timesCalledBetweenExecutions = 0;