j2k: flatten test cases and testData directory structure

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

j2k/testData/fileOrElement/for/forThroughNonArrayIndices.kt

@@ -0,0 +1,11 @@
+class X {
+    public var length: Int = 5
+}
+
+class C {
+    fun foo(x: X) {
+        for (i in 0..x.length - 1) {
+            System.out.print(i)
+        }
+    }
+}