evolve: mark new hash-salting extras keys as uninteresting for effect flag

The user doesn't care if the evolve_source_local/evolve_source_other values in the extras changed, so this patch adds them to the blacklist that already exists for that purpose.

This should also fix the flakiness we've seen in some tests. The flakiness seemed to stem from mercurial.obsutil.geteffectflag() not sorting extras keys. That means we ran into it relatively often for the evolve_source_local/evolve_source_other keys because there were two of them. That sorting bug should be fixed upstream.