A simpler ActorRefProvider config #20649 (#20767)

* Provide shorter aliases for the ActorRefProviders #20649
* Use the new actorefprovider aliases throughout code and docs
* Cleaner alias replacement logic

akka-remote/src/test/scala/akka/remote/RemoteWatcherSpec.scala

@@ -66,7 +66,7 @@ class RemoteWatcherSpec extends AkkaSpec(
   """akka {
        loglevel = INFO
        log-dead-letters-during-shutdown = false
-       actor.provider = "akka.remote.RemoteActorRefProvider"
+       actor.provider = remote
        remote.netty.tcp {
          hostname = localhost
          port = 0