j2k: flatten test cases and testData directory structure

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

j2k/testData/fileOrElement/constructors/artificialPrimary.java

@@ -0,0 +1,13 @@
+public class Test {
+  private final String s;
+  boolean b;
+  double d;
+
+  public Test() {
+    b = true;
+  }
+
+  public Test(String s) {
+    this.s = s;
+  }
+}