Merge boxWithStdlib testData into box, delete BoxWithStdlib test

compiler/testData/codegen/box/reflection/mapping/fakeOverrides/javaFieldGetterSetter.kt

@@ -0,0 +1,23 @@
+// WITH_REFLECT
+// KT-8131 Cannot find backing field in ancestor class via reflection
+
+import kotlin.reflect.*
+import kotlin.reflect.jvm.*
+
+open class TestBase {
+    var id = 0L
+}
+
+class TestChild : TestBase()
+
+fun box(): String {
+    val property = TestChild::class.memberProperties.first { it.name == "id" } as KMutableProperty<*>
+    if (property.javaField == null)
+        return "Fail: no field"
+    if (property.javaGetter == null)
+        return "Fail: no getter"
+    if (property.javaSetter == null)
+        return "Fail: no setter"
+
+    return "OK"
+}