Akka.Cluster.Tools: ClusterSingleton should factor in AppVersion when choosing next likely home for messages during deployments

[Aaronontheweb]

Is your feature request related to a problem? Please describe.

Akka.Cluster.Sharding does this currently - shards are homed onto nodes with the highest AppVersion when a deployment is detected inside the cluster. This helps us guarantee that we aren't allocating shards, again, on locations that are going to be removed later during a deployment.

We do not do this for Akka.Cluster singletons, which have the same issue as sharded entity actors: they prefer to be moved only once if possible.

Describe the solution you'd like

Consider AppVersion in the re-homing calculation for cluster singletons.