evolve: load evolvestate before passing to continueevolve() This patch moves some code from continueevolve() to evolve() function so that we have a loaded evolvestate present in the evolve() function for post processing.

evolve: move the handling for non-continue part in else conditional This will help us do factor out which operations we want to do for continue, which for non-continue and which operations we want to do for both of them.

evolve: move the logic of continuation handling of `hg evolve` in own fn The function which defines the evolve command is pretty big with all the logic messed up there. It's better to have individual functions for individual uses. The movement of code will help in adding more logic to continue part in clean way. Moreover for implementing `hg continue`, we need all continuation handling in their own functions, so it will help there too.