SE-0428: Resolve DistributedActor protocols

[jaleel (Jaleel Akbashev)]

@ktoso

Resolvable -- i.e. it is a protocol i can resolve()

@Douglas_Gregor have a fair point and Resolvable indeed fits perfectly and feels a bit more swifty, though still could be a bit confused on what exactly it resolves. I mean imagine checking documentation and you see Resolvable—would take some time to realise it’s exactly this, IMHO.