Move blackBoxFile() testData to box/ directory

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

compiler/testData/codegen/box/properties/kt1168.kt

@@ -0,0 +1,15 @@
+public abstract class BaseClass() {
+    protected abstract val kind : String
+
+    protected open val kind2 : String = " kind1"
+
+    fun debug() = kind + kind2
+}
+
+public class Subclass : BaseClass() {
+    override val kind : String = "Physical"
+
+    override val kind2 : String = " kind2"
+}
+
+fun box():String = if(Subclass().debug() == "Physical kind2") "OK" else "fail"