evolve: always order the revs to be evolved The current code only order the revs if we are resolving orphans and not in other case. The ordering is important when we pass --all and tackle multiple occurence of the same instability. Let's order the revs for each instability. There are enough test coverage of phase-divergence and content-divergence that I feel confident doing it because none of the test changed. The change in test-evolve-content-divergent.t demonstrates the indeed ordering helped.

tests: add test of resolution of content-divergent stacks This patch adds a test of resolution of content-divergence stacks where a series of changesets get mutated as two different series resulting in whole content-divergent stacks. As the tests shows, we are not processing the changesets in right order which needs to be fixed first.