brpc添加redis sentinel支持

brpc支持从redis sentinel获取redis server, 提高可用性
目前想到的是新增 NamingService, 可以是订阅频道的方式, 也可以是周期性获取的方式, 但是sentinel一般是ip/url:port的形式提供, 这样好像无法传入load_balancer, 同时也就无法使用naming_service? 我看只有有load_balancer时才用naming_service, 好像陷入了矛盾

Start by tracing brpc's NamingService and load_balancer integration, which the issue identifies as the central constraint. Compare the proposed subscription and periodic-fetch approaches for Redis Sentinel; done means Sentinel endpoints can provide a usable Redis server while fitting brpc's naming and load-balancing model.

Written by the indexing model from the issue text.