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/Application.hpp

@@ -68,6 +68,7 @@ public:
     virtual HighlightController *getHighlights() = 0;
     virtual NotificationController *getNotifications() = 0;
     virtual ITwitchIrcServer *getTwitch() = 0;
+    virtual PubSub *getTwitchPubSub() = 0;
     virtual Logging *getChatLogger() = 0;
     virtual ChatterinoBadges *getChatterinoBadges() = 0;
     virtual FfzBadges *getFfzBadges() = 0;
@@ -97,6 +98,12 @@ public:
     Application &operator=(const Application &) = delete;
     Application &operator=(Application &&) = delete;
 
+    /**
+     * In the interim, before we remove _exit(0); from RunGui.cpp,
+     * this will destroy things we know can be destroyed
+     */
+    void fakeDtor();
+
     void initialize(Settings &settings, Paths &paths);
     void load();
     void save();
@@ -128,6 +135,7 @@ public:
 
 private:
     TwitchLiveController *const twitchLiveController{};
+    std::unique_ptr<PubSub> twitchPubSub;
     const std::unique_ptr<Logging> logging;
 
 public:
@@ -181,6 +189,7 @@ public:
         return this->highlights;
     }
     ITwitchIrcServer *getTwitch() override;
+    PubSub *getTwitchPubSub() override;
     Logging *getChatLogger() override;
     ChatterinoBadges *getChatterinoBadges() override
     {