Merge boxWithStdlib testData into box, delete BoxWithStdlib test

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

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