Consider using an asynchronous logback appender

[ljdelight]

I happened to see that the logback config, at least for production, should be using an async appender to avoid performance issues. Maybe it doesn't matter so much since the prod logback is set to stdout, either way, needs looking into.

See https://doc.akka.io/docs/akka/current/typed/logging.html#slf4j-backend

Warning

For production the SLF4J backend should be configured with an asynchronous appender as described here. Otherwise there is a risk of reduced performance and thread starvation problems of the dispatchers that are running actors and other tasks.

[ljdelight]

Resolved in #1088