Tweak Type#atoms to normalize first

TypeComparer's compareAtoms assumes it has an answer to subtyping if one
of the types has atoms and the other doesn't.  But an unreduced match
alias won't have atoms, so we shouldn't bail early.

Author: dwijnand

compiler/src/dotty/tools/dotc/core/Types.scala

@@ -1373,7 +1373,7 @@ object Types {
           Atoms.Range(set, set)
         else Atoms.Unknown
 
-      dealias match
+      dealias.normalized match
         case tp: SingletonType =>
           tp.underlying.atoms match
             case as @ Atoms.Range(lo, hi) =>