evolve: write data to evolvestate in case on conflicts in phase-divergence This patch makes phase-divergence resolution write data to evolvestate instead of graftstate. The `evolve --continue` handling of phase-divergence is broken which will be done in upcoming patches.

evolve: explicitly turn revs to list before storing into evolvestate The cbor library which we are using cannot handle encoding and decoding Python sets, and revs was set there. Let's convert revs explicitly to list to make sure we don't try writing sets.

tests: add tests of content+parent change creating phase-divergence This patch adds tests which shows handling of phase divergence cases by `hg evolve` command which involved content+parent change. The conflicts case is not handled and will be fixed in upcoming patches.