Note [Scoped tyvars in a TcTyCon]

The tcTyConScopedTyVars field records the lexicial-binding connection
between the original, user-specified Name (i.e. thing in scope) and
the TcTyVar that the Name is bound to.

Order *does* matter; the tcTyConScopedTyVars list consists of
     specified_tvs ++ required_tvs

where
   * specified ones first
   * required_tvs the same as tyConTyVars
   * tyConArity = length required_tvs

tcTyConScopedTyVars are used only for MonoTcTyCons, not PolyTcTyCons.
See Note [TcTyCon, MonoTcTyCon, and PolyTcTyCon] in GHC.Tc.TyCl