Migrate boxWithJava tests to multi-file framework

compiler/testData/codegen/boxWithJava/companionObjectAccessor.kt

@@ -0,0 +1,27 @@
+// FILE: J.java
+
+public class J {
+    public static int f() {
+       return A.Companion.getI1() + A.Companion.getI2() + B.Named.getI1() + B.Named.getI2();
+    }
+}
+
+// FILE: test.kt
+
+class A {
+    companion object {
+        val i1 = 1
+        val i2 = 2
+    }
+}
+
+class B {
+    companion object Named {
+        val i1 = 3
+        val i2 = 4
+    }
+}
+
+fun box(): String {
+    return if (J.f() == A.i1 + A.i2 + B.i1 + B.i2) "OK" else "Fail: ${J.f()}"
+}