topic: preserve topic during evolve previously, topic handling was absent leading to whatever the active topic was when `hg evolve` was run to be used for all evolve results

topic: 'hg evolve --all' pick all trouble within current topic This is the first changeset of a collaboration between the topic extensions and evolve. If there is an active topic, 'hg evolve --all' will try to fix all changesets in that topic wherever they are. Aspiring descendant that are not in the current topic will be ignored. For now, evolve behave as usual if there is no active topic. This is a bit inconsistent and will probably be unified in the future.