ReifiedListIterator can be a PredictiveIterator
ReifiedListIterator can be a PredictiveIterator

Since the list is already reified, we know how many elements there are.
This is a significant speedup for things like `$foo.split(/\s+/).elems`
as it can just return the elements of the list (in fact, the `.elems`
part is now fully inlined into the caller).

labster/rakudo,nbrown/rakudo,softmoth/rakudo,MasterDuke17/rakudo,salortiz/rakudo,tbrowder/rakudo,MasterDuke17/rakudo,rakudo/rakudo,tony-o/rakudo,salortiz/rakudo,rakudo/rakudo,nbrown/rakudo,salortiz/rakudo,labster/rakudo,tbrowder/rakudo,salortiz/rakudo,MasterDuke17/rakudo,softmoth/rakudo,tbrowder/rakudo,softmoth/rakudo,tony-o/rakudo,labster/rakudo,tony-o/rakudo,softmoth/rakudo,rakudo/rakudo,rakudo/rakudo,MasterDuke17/rakudo,tony-o/rakudo,nbrown/rakudo,MasterDuke17/rakudo,tony-o/rakudo,tbrowder/rakudo,labster/rakudo,rakudo/rakudo,salortiz/rakudo,nbrown/rakudo,softmoth/rakudo,labster/rakudo,nbrown/rakudo,rakudo/rakudo,tbrowder/rakudo,salortiz/rakudo,MasterDuke17/rakudo,labster/rakudo,tony-o/rakudo,tbrowder/rakudo,nbrown/rakudo