Migrate boxAgainstJava tests to multi-file framework

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

@@ -1,4 +1,21 @@
-import test.staticField as E
+// FILE: test/E.java
+
+package test;
+
+import java.util.Set;
+import java.util.EnumSet;
+
+public enum E {
+    INSTANCE;
+    
+    public static int foo = 42;
+    
+    public static final Set<E> INSTANCES = EnumSet.of(INSTANCE);
+}
+
+// FILE: 1.kt
+
+import test.E
 
 fun box(): String {
     val instances = E.INSTANCES