j2k: flatten test cases and testData directory structure

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

j2k/testData/fileOrElement/class/kt-639.java

@@ -0,0 +1,18 @@
+package demo;
+
+import java.util.HashMap;
+
+class Test {
+  Test() {  }
+  Test(String s) {  }
+}
+
+class User {
+  void main() {
+    HashMap m = new HashMap(1);
+    HashMap m2 = new HashMap(10);
+
+    Test t1 = new Test();
+    Test t2 = new Test("");
+  }
+}