Merge boxWithStdlib testData into box, delete BoxWithStdlib test

compiler/testData/codegen/box/reflection/call/fakeOverride.kt

@@ -0,0 +1,12 @@
+// WITH_REFLECT
+
+open class A {
+    fun foo() = "OK"
+}
+
+class B : A()
+
+fun box(): String {
+    val foo = B::class.members.single { it.name == "foo" }
+    return foo.call(B()) as String
+}