j2k: flatten test cases and testData directory structure

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

j2k/testData/fileOrElement/mutableCollections/Recursion.kt

@@ -0,0 +1,15 @@
+import java.util.*
+
+class A {
+    fun foo(collection: MutableCollection<String>) {
+        bar(collection)
+    }
+
+    fun bar(collection: MutableCollection<String>) {
+        if (collection.size() < 5) {
+            foo(collection)
+        } else {
+            collection.add("a")
+        }
+    }
+}