Migrate boxAgainstJava tests to multi-file framework

compiler/testData/codegen/boxAgainstJava/visibility/package/packageFun.kt

@@ -1,5 +1,17 @@
+// FILE: protectedPack/J.java
+
+package protectedPack;
+
+public class J {
+    String test() {
+        return "OK";
+    }
+}
+
+// FILE: 1.kt
+
 package protectedPack
 
 fun box(): String {
-   return packageFun().test()!!
+    return J().test()!!
 }