Move IntFunction to scala and don't allow throwing

Author: mdedetrich

actor/src/main/java/org/apache/pekko/japi/function/IntFunction.java

@@ -152,3 +152,10 @@ trait Creator[+T] extends Serializable {
   @throws(classOf[Exception])
   def create(): T
 }
+
+@nowarn("msg=@SerialVersionUID has no effect")
+@SerialVersionUID(1L)
+@FunctionalInterface
+trait IntFunction[T] extends Serializable {
+  def apply(value: Int): T
+}