Update the evolution helpers function to support both old-style configuration and
new-style configuration:
experimental.evolution=all is renamed into experimental.evolution=true experimental.evolution=createmarkers is renamed into experimental.evolution.createmarkers=true experimental.evolution=allowunstable is renamed into experimental.evolution.allowunstable=true experimental.evolution=exchange is renamed into experimental.evolution.exchange=true
We choose to not rename individual config options; keeping the same names
would easy the transition for users but it's something that could be easily
done in the future.
It feels like we should automatically enable createmarkers in this scenario instead of being user hostile. But this can be done as a follow-up.