refactor: Twitch PubSub client (#5059)

* Remove unused `setAccountData` function

* Move PubSub out of TwitchIrcServer and into Application

* Add changelog entry

* fix: assert feedback

* Add PubSub::unlistenPrefix as per review suggestion

* Fix tests

* quit pubsub on exit

might conflict with exit removal, so can be reverted but this shows it's possible

* Don't manually call stop on clients, it's called when the connection is closed

* nit: rename `mainThread` to `thread`

* Join in a thread!!!!!!!!

src/providers/twitch/PubSubClient.hpp

@@ -70,6 +70,7 @@ private:
     std::atomic<bool> awaitingPong_{false};
     std::atomic<bool> started_{false};
 
+    std::shared_ptr<boost::asio::steady_timer> heartbeatTimer_;
     const PubSubClientOptions &clientOptions_;
 };