Move blackBoxFile() testData to box/ directory

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

compiler/testData/codegen/box/closures/enclosingLocalVariable.kt

@@ -0,0 +1,8 @@
+fun box() : String {
+    val cl = 39
+    return if (sum(200, { val m = { val r = { cl };  r() }; m() }) == 239) "OK" else "FAIL"
+}
+
+fun sum(arg:Int, f :  () -> Int) : Int {
+    return arg + f()
+}