Move storage of LifecycleWatch into DistributedActorContext #926
Description
DistributedActorContext is the new ActorContext where we can store state for distributed actors.
It is internal only and stored inside the actor's identity.
The reason this matters is because today we're hitting a horrible hack to store all lifecycles in a hashmap in the actor system, but they should be in the identity instead, as they are "per actor".
State is to be initialized during actorRady