Active HC and outlier detection events remote sink

Define and implement HC and outlier detection event gRPC streaming to a remote endpoint

Description: It would be nice to have an ability to stream active healthcheck and outlier detection events into some sort of remote gRPC service. For now, only file sinks are available. Having gRPC interface would allow having unified reporting infrastructure, i.e. report everything to gRPC endpoints, instead of having gRPC endpoint for access logs, but some log collector agent+log rotation for events