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!!!!!!!!

mocks/include/mocks/EmptyApplication.hpp

@@ -104,6 +104,12 @@ public:
         return nullptr;
     }
 
+    PubSub *getTwitchPubSub() override
+    {
+        assert(false && "getTwitchPubSub was called without being initialized");
+        return nullptr;
+    }
+
     Logging *getChatLogger() override
     {
         assert(!"getChatLogger was called without being initialized");