Move blackBoxFile() testData to box/ directory

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

compiler/testData/codegen/box/controlStructures/kt2291.kt

@@ -0,0 +1,6 @@
+fun box(): String {
+  1 in 1.rangeTo(10)
+  1..10
+  'h' in 'A'.rangeTo('Z')
+  return "OK"
+}