j2k: flatten test cases and testData directory structure

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

j2k/testData/fileOrElement/thisExpression/classAdotThisFoo.java

@@ -0,0 +1,14 @@
+//file
+package a.b
+
+class Base {
+  void foo() {}
+}
+
+class A extends Base {
+  class C {
+    void test() {
+      A.this.foo();
+    }
+  }
+}