_descendant: use filteredset instead of orderedlazyset The orderedlazyset class is going away. Filteredset gives the same service.

addset: use the base implementation for ascending and descending

addset: use base implementation for __filter__

addset: use base implementation for __add__

addset: use base implementation for __sub__

addset: use base implementation for __and__

addset: promote to real smartset Better revset performance are also achieved with less overlay. There is no good reason for addset to not be a smartset. We can replace the `_orderedsetmixin` inheritance since `abstractsmartset` has efficient min and max too.

addset: add a __nonzero__ method This is required to be a full smartset (not sure what was happening before that...)

addset: offer a fastasc and fastdesc methods If the underlying object offers fast iterators, we use them to provide fast iterators too.

addset: split simple and ordered iteration We have two goals here. First, we would like to restore the former iteration order we had in 2.9. Second, we want this logic to be reusable for `fastasc` and `fastdesc` methods.