j2k: flatten test cases and testData directory structure

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

j2k/testData/fileOrElement/constructors/fieldsInitializedFromParams6.java

@@ -0,0 +1,7 @@
+class C {
+    public Object x;
+
+    public C(String x) {
+        this.x = x;
+    }
+}