Migrate boxWithJava tests to multi-file framework

compiler/testData/codegen/boxWithJava/jvmOverloads/generics.kt

@@ -0,0 +1,18 @@
+// FILE: Test.java
+
+public class Test {
+    public static String invokeMethodWithOverloads() {
+        C<String> c = new C<String>();
+        return c.foo("O");
+    }
+}
+
+// FILE: generics.kt
+
+class C<T> {
+    @kotlin.jvm.JvmOverloads public fun foo(o: T, k: String = "K"): String = o.toString() + k
+}
+
+fun box(): String {
+    return Test.invokeMethodWithOverloads()
+}