[Accepted] SE-0344: Distributed Actor Runtime

Hi everyone. The second review of SE-0344: Distributed Actor Runtime ended on March 31, 2021. The core team has decided to accept this proposal. This second revision incorporated feedback from the first round of review, making the initialization of a distributed actor instance's actorSystem explicit inside non-delegating initializers, and turning the RemoteCallTarget type for identifying methods when sending remote messages into a fully opaque type. The core team is satisfied with the way the proposal addressed the first review's feedback, and we did not receive any public feedback during the second review. Thank you to the authors for incorporating the feedback, and thank you to everyone in the community who helped shape this proposal!