Migrate boxAgainstJava tests to multi-file framework

compiler/testData/codegen/boxAgainstJava/enum/simpleJavaEnumWithFunction.kt

@@ -1,4 +1,27 @@
-import test.simpleJavaEnumWithFunction.*
+// FILE: test/En.java
+
+package test;
+
+import java.lang.Override;
+import java.lang.String;
+
+public enum En {
+    A {
+        @Override
+        public String repr() {
+            return "A";
+        }
+    },
+    B;
+    
+    public String repr() {
+        return "ololol" + toString();
+    }
+}
+
+// FILE: 1.kt
+
+import test.En.*
 
 fun box() =
     if (A.repr() == "A" && B.repr() == "olololB") "OK"