j2k: flatten test cases and testData directory structure

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

j2k/testData/fileOrElement/function/synchronizedMethod.java

@@ -0,0 +1,8 @@
+class A {
+    synchronized void foo() {
+        bar();
+    }
+
+    void bar() {
+    }
+}