addset: drop caching through generatorset

The utility of this cache is debatable (no visible benchmark impact) and using
generatorset for such purpose makes the code complicated.

We drop it for now. Someone can reintroduce a smart version of it in the future
if it is detected to be relevant.

mercurial/revset.py

@@ -2499,7 +2499,6 class addset(abstractsmartset):
         If the ascending attribute is set, iterate over both collections at the
         same time, yielding only one value at a time in the given order.
         """
-        if not self._iter:
             if self._ascending is None:
                 def gen():
                     for r in self._r1:
@@ -2513,8 +2512,7 class addset(abstractsmartset):
                 iter1 = iter(self._r1)
                 iter2 = iter(self._r2)
                 gen = self._iterordered(self._ascending, iter1, iter2)
-            self._iter = generatorset(gen)
-        return self._iter
+        return gen
 
     def __iter__(self):
         if self._genlist: