Reapply "refactor: JMeterSerialTest to Kotlin so we have one less compileJava task"

This reverts commit 8a5f5d8.

Author: vlsi

src/jorphan/src/testFixtures/kotlin/org/apache/jorphan/test/JMeterSerialTest.kt

@@ -15,17 +15,16 @@
  * limitations under the License.
  */
 
-package org.apache.jorphan.test;
+package org.apache.jorphan.test
 
-import org.junit.jupiter.api.parallel.Execution;
-import org.junit.jupiter.api.parallel.ExecutionMode;
-import org.junit.jupiter.api.parallel.Isolated;
+import org.junit.jupiter.api.parallel.Execution
+import org.junit.jupiter.api.parallel.ExecutionMode
+import org.junit.jupiter.api.parallel.Isolated
 
 /**
  * Used to tag tests which need to be run on their own (in serial) because
  * either, they cause other tests to fail, or they fail when run in parallel.
  */
 @Isolated
 @Execution(ExecutionMode.SAME_THREAD)
-public interface JMeterSerialTest {
-}
+interface JMeterSerialTest