Consider `ActorExitStatus::Quit` as a successful exit?

Currently, an exit with a status different from Success will generate a log error, and the state ends up as ActorState::Failure.

The code is like this:

  if !exit_status.is_success() {
      error!(actor_name=self.actor_instance_id(), actor_exit_status=?exit_status, "actor-failure");
  }
self.actor_state.exit(exit_status.is_success());

But, the happy path can only happen if all mailboxes are dropped (except the one owned by the context). Taking care of dropping all mailboxes is a bit of a chore and is error-prone.

Another way to gracefully shutdown an actor is by calling actor_handle.quit(), this is a nice way to stop an actor, unfortunately, it generates an ERROR log and the actor state will become Actor::Failure which can misleading. We could consider this as a successful operation and not log an ERROR and have a final state Actor::Success.

Search the Rust codebase for the shown exit_status.is_success() branch and ActorExitStatus::Quit, then read how actor_handle.quit() affects ActorState. Done means quit exits no longer log an ERROR and leave the actor in a failure state, with behavior verified by the relevant existing actor tests if available.