Simplify SetupDaemonConfig API

[miparnisari]

This function really really shouldn't accept a concrete instance of a logrus.Logger. This should be an interface and, if consumers want, they can pass their own implementation (or a NoOpLogger)

Something else I noticed: it is really really easy for consumers of this project to simply do gubernator.SpawnDaemon(ctx, DaemonConfig{GRPCListenAddress: "localhost:8111"}) - this will set all other configs to their zero values! 😱

Originally posted by @miparnisari in #214 (comment)