Enrich Dex logs with real IP and request ID (#3661)

cmd/dex/config.go

cmd/dex/logger.go

cmd/dex/serve.go

examples/config-dev.yaml

server/deviceflowhandlers.go

server/handlers.go

server/introspectionhandler.go

server/introspectionhandler_test.go

server/oauth2.go

server/refreshhandlers.go

server/server.go