Merge sample/api folders for Korro

[Jolanrensen]

Code samples for the documentation website reside in core/.../test/.../samples/api,
and tests/.../samples/api
and they are copied over to Markdown files in docs/StardustDocs/topics
by Korro.

What I do not know is why we have two separate folders for these samples. It's a bit confusing, so unless we have a reason not to, we should probably merge the two.