=sam #12702 Create FsmSimpleRedelivery sample

This one is created instead of the batching pattern of #12702, as suggested by @ktoso in #12702's discussion.

Should it get some tests, as stated in `CONTRIBUTING.md`? I'm asking, because most other samples seem not to be tested at all. =)

Also, I'm not quite sure why Scalariform did not change `=>` into its UTF-8 counterpart. Sbt says it is running it at each compilation...
I'm tempted to call it `SimpleOrderedReveliderer` or `NaiveRedeliverer` or something like this.

Something to make users aware that this is a simple example, not a prod ready pattern.
We're also working on an "at least once" trait, that can be out of order etc - https://github.com/akka/akka/issues/15327