Migrate boxWithJava tests to multi-file framework

compiler/testData/codegen/java8/box/defaultMethodCallViaInterface.kt

@@ -0,0 +1,23 @@
+// FILE: Simple.java
+
+public interface Simple {
+    default String test(String s) {
+        return s + "K";
+    }
+
+    static String testStatic(String s) {
+        return s + "K";
+    }
+}
+
+// FILE: main.kt
+
+interface TestInterface : Simple {}
+class Test : TestInterface {}
+
+fun box(): String {
+    val test = Test().test("O")
+    if (test != "OK") return "fail $test"
+
+    return Simple.testStatic("O")
+}