Move blackBoxFile() testData to box/ directory

Delete all test methods (and empty test classes), since they'll be
auto-generated

compiler/testData/codegen/box/functions/nothisnoclosure.kt

@@ -0,0 +1,15 @@
+fun foo(x: Int) {}
+
+fun loop(var times : Int) {
+   while(times > 0) {
+        val u : (value : Int) -> Unit = {
+            foo(it)
+        }
+        u(times--)
+   }
+}
+
+fun box() : String {
+    loop(5)
+    return "OK"
+}