fixes #25419; lift magic types to typeclasses

[ringabout]

fixes #25419

[Araq]

What about tyOpenArray, tyVarargs, etc?

[ringabout]

 # we fill it out later. For magic generics like 'seq', it won't be filled
  # so we use tyNone instead of nil to not crash for strange conversions
  # like: mydata.seq
  if s.typ.kind in {tyOpenArray, tyVarargs} and s.typ.len == 1:
    # XXX investigate why `tySequence` cannot be added here for now.
    discard
  else:
    rawAddSon(s.typ, newTypeS(tyNone, c))

tyOpenArray, tyVarargs was special cased here

[github-actions]

Thanks for your hard work on this PR!
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