Move blackBoxFile() testData to box/ directory

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

compiler/testData/codegen/box/traits/withRequired.kt

@@ -0,0 +1,15 @@
+open class AL<T> {
+    fun get(index: Int) : T? = null
+}
+
+trait ALE<T> : AL<T> {
+    fun getOrValue(index: Int, value : T) : T = get(index) ?: value
+}
+
+class SmartArrayList() : ALE<String>, AL<String>() {
+}
+
+fun box() : String {
+  val c = SmartArrayList()
+  return if("239" == c.getOrValue(0, "239")) "OK" else "fail"
+}