j2k: flatten test cases and testData directory structure

Move j2k/test/tests -> j2k/tests, j2k/test/testData -> j2k/testData

j2k/testData/fileOrElement/enum/runnableImplementation.java

@@ -0,0 +1,9 @@
+//class
+enum Color implements Runnable {
+  WHITE, BLACK, RED, YELLOW, BLUE;
+
+  public void run() {
+   System.out.println("name()=" + name() +
+       ", toString()=" + toString());
+  }
+}