feat: consolidating AddHandler for RPC interface

[jgkawell]

This PR consolidates the functionality of the AddHandler and reflection methods in the RPC interface within the chassis. The previous setup required a few different calls for the same amount of work and didn't support gRPC servers (as opposed to ConnectRPC) very well. The new pattern simplifies things so that you can do the following:

// for ConnectRPC
pattern, handler := kvConnect.NewKeyValueServiceHandler(h)
server.AddHandler(pattern, handler, true)

// for gRPC
grpcServer := server.GetGrpcServer()
discoverygrpc.RegisterAggregatedDiscoveryServiceServer(grpcServer, c.xDSServer)
server.AddHandler("/envoy.service.discovery.v3.AggregatedDiscoveryService/", grpcServer, false)

I also removed the logger access as this shouldn't be managed at this layer. It should be managed at the handler layer instead and injected down from main() at instantiation.