Move blackBoxFile() testData to box/ directory

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

compiler/testData/codegen/box/arrays/kt950.kt

@@ -0,0 +1,9 @@
+import java.util.*
+
+fun <K, V> MutableMap<K, V>.set(k : K, v : V) = put(k, v)
+
+fun box() : String {
+    val map = HashMap<String,String>()
+    map["239"] = "932"
+    return if(map["239"] == "932") "OK" else "fail"
+}