j2k: flatten test cases and testData directory structure

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

j2k/testData/fileOrElement/for/forThroughNonCollectionIndices.java

@@ -0,0 +1,11 @@
+class X {
+    public int size() { return 5; }
+}
+
+class C{
+    void foo(X x) {
+        for (int i = 0; i < x.size(); i++) {
+            System.out.print(i);
+        }
+    }
+}