evolve: add logic to continue interrupted content-divergence resolution We continue the interrupted content-divergence using the logic to complete content-divergence which we refactored in it's own function few patches ago. We had to delete evolvestate file before using cmdutil.amend() because otherwise we can't use the function. This leads to a hack which deletes the evolvestate file, we may want to not to use the high level API function here. Also we had to pass evolvestate also to _completecontentdivergent function because of this. This patch also, adds a test which demonstrates that the logic works fine.

evolve: store the evolvestate file when encountering conflicts This patch makes `hg evolve` store the evolvestate file when it encounters merge conflicts while resolving content-divergence.

evolve: take out logic to complete phase-divergence in separate fn This patch takes out the logic to complete the content-divergence resolution to it's own separate function so that we can reuse it in case of interrupted resolution.