j2k: flatten test cases and testData directory structure

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

j2k/testData/fileOrElement/constructors/fieldsInitializedFromParams7.java

@@ -0,0 +1,9 @@
+class C {
+    public Object x;
+
+    public C(Object x, boolean b) {
+        if (b) {
+            this.x = x;
+        }
+    }
+}