Fix NameKinds
Fix NameKinds

The previous change hid the refinements of `info` and apply/unapply.
Turning SimpleNameKind and SignedNameKind back into objects fixes that.
Neither name kind installs anything as a side effect so turning them into
objects is OK.

lampepfl/dotty,som-snytt/dotty,som-snytt/dotty,lampepfl/dotty,lampepfl/dotty,dotty-staging/dotty,lampepfl/dotty,dotty-staging/dotty,dotty-staging/dotty,sjrd/dotty,som-snytt/dotty,lampepfl/dotty,dotty-staging/dotty,dotty-staging/dotty,sjrd/dotty,sjrd/dotty,som-snytt/dotty,som-snytt/dotty,sjrd/dotty,sjrd/dotty