Merge boxMultiFile testData into box, delete BoxMultiFile test

compiler/testData/codegen/box/multifileClasses/constPropertyReferenceFromMultifileClass.kt

@@ -0,0 +1,27 @@
+// WITH_RUNTIME
+// FILE: 1.kt
+
+import a.OK
+
+fun box(): String {
+    val okRef = ::OK
+
+    // TODO: see KT-10892
+//    val annotations = okRef.annotations
+//    val numAnnotations = annotations.size
+//    if (numAnnotations != 1) {
+//        return "Failed, annotations: $annotations"
+//    }
+
+    return okRef.get()
+}
+
+// FILE: 2.kt
+
+@file:[JvmName("MultifileClass") JvmMultifileClass]
+package a
+
+annotation class A
+
+@A
+const val OK: String = "OK"