Move blackBoxFile() testData to box/ directory

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

compiler/testData/codegen/box/super/basicmethodSuperTrait.kt

@@ -0,0 +1,15 @@
+import java.util.ArrayList
+
+trait Tr {
+   fun extra() : String = "_"
+}
+
+class N() : Tr {
+   override fun extra() : String = super<Tr>.extra() + super<Tr>.extra()
+}
+
+fun box(): String {
+    val n = N()
+    if (n.extra() == "__") return "OK"
+    return "fail";
+}