j2k: flatten test cases and testData directory structure

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

j2k/testData/fileOrElement/constructors/fieldsInitializedFromParams3.kt

@@ -0,0 +1,10 @@
+class C(p: Int) {
+    private val p: Int
+
+    {
+        var p = p
+        this.p = p
+        System.out.println(p++)
+        System.out.println(p)
+    }
+}