j2k: flatten test cases and testData directory structure

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

j2k/testData/fileOrElement/constructors/privateConstructors.java

@@ -0,0 +1,12 @@
+class C {
+  private C(int arg1, int arg2, int arg3) {
+  }
+
+  private C(int arg1, int arg2) {
+    this(arg1, arg2, 0);
+  }
+
+  public C(int arg1) {
+    this(arg1, 0, 0);
+  }
+}