FutureConverters `toJava` and `toScala` should be `asJava` and `asScala` if they only wrap

[SethTisue]

we normally use as for wrappers and to for things that convert by copying

(FutureConverters and perhaps elsewhere, audit needed)

[SethTisue]

volunteer to add the new names and deprecate the old names?

[lrytz]

Argh, missed this while migrating the converters to 2.13 std lib. I'll fix it in RC3 if there's one.

[SethTisue]

@lrytz did this end up being addressed?

[lrytz]

From @NthPortal with ❤️ scala/scala#8094