This PR allows a simple derives call to work on Scala 3 enums.

We add a new macroRWAll macro, that derives now forwards to. This can be called once on each sealed trait or enum and will automatically generate the macroR calls on all the sub-classes. We then add a pair of superTypeReader/superTypeWriter forwarders to allow sub-classes to make use of super-class readers and writers automatically without any input from the user.

Note that this approach does not work in Scala 2; while macroRWAll can be defined, superTypeReader/superTypeWriter seem to cause diverging implicit expansions. So for now I leave the Scala 2 experience unchanged