evolve: handle interrupted phase-divergence resolution gracefully This patch adds logic to handle the interrupted phase-divergence resolution by `hg evolve` command gracefully. We first complete the relocation of the changeset and then do the divergence resolution. Previous functions moved required code separate fucntions so that we can use them here.

evolve: move logic to resolve phase-divergence in a new function This patch moves logic which does the revert and create a commit on top of public changeset because we need to repeat that logic while handling continuation of `hg evolve` when there are conflicts while rebasing the phase-divergent changeset.

evolve: store the precursor of phase-divergent in evolvestate This patch makes `hg evolve` store the precursor of phase-divergent changeset in evolvestate so that we don't need to calculate that again.

evolve: move logic to complete interrupted relocation to new fn This moves logic which completed the interrupted relocation to it's own separate function as we will need that function in continuing phase-divergence and content-divergence too.

evolve: move logic to complete interrupted orphan resolution to new fn This patch moves logic which completes an interrupted orphan resolution to it's own new function. We will defining such functions for completing phase-divergence and content-divergence too.

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.