Migrate boxAgainstJava tests to multi-file framework

compiler/testData/codegen/boxAgainstJava/innerClass/kt3532.kt

@@ -1,4 +1,12 @@
+// FILE: Foo.java
+
+public class Foo {
+    public class Inner { }
+}
+
+// FILE: 1.kt
+
 fun box(): String {
-    kt3532().Inner()
+    Foo().Inner()
     return "OK"
-}
+}