j2k: flatten test cases and testData directory structure

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

j2k/testData/fileOrElement/dropAccessors/DataClass.kt

@@ -0,0 +1,6 @@
+public class Test(public var id: String?, public val name: String, public val age: Int) {
+
+    {
+        System.out.println(age)
+    }
+}