j2k: flatten test cases and testData directory structure

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

j2k/testData/fileOrElement/constructors/fieldsInitializedFromParams8.java

@@ -0,0 +1,12 @@
+class Base {
+    Base(Object o, int l){}
+}
+
+class C extends Base {
+    private final String string;
+
+    public C(String s) {
+        super(s, s.length());
+        this.string = s;
+    }
+}