j2k: flatten test cases and testData directory structure

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

j2k/testData/fileOrElement/annotations/jetbrainsNullable.kt

@@ -0,0 +1,27 @@
+// !specifyLocalVariableTypeByDefault: true
+package test
+
+public class Test(str: String?) {
+    var myStr: String? = "String2"
+
+    {
+        myStr = str
+    }
+
+    public fun sout(str: String?) {
+        System.out.println(str)
+    }
+
+    public fun dummy(str: String?): String? {
+        return str
+    }
+
+    public fun test() {
+        sout("String")
+        val test: String? = "String2"
+        sout(test)
+        sout(dummy(test))
+
+        Test(test)
+    }
+}