Redis PubSub disconnecting resets channels

[SystemUpdate]

The RedisBungee API offers an API for plugins to register their own channels and then use the PubSubMessageEvent however if the pubsub throws an error, it won't register what channels external plugins did and doesn't provide a way for plugins to know of an error that caused its channel to be unregistered.

I propose that channels registered by plugins are stored in a set that can be used to register those channels when the PubSub recovers