refactor: turn StreamerMode into a singleton(-like thing) (#5216)

src/singletons/Settings.hpp

@@ -15,7 +15,6 @@
 #include "controllers/sound/ISoundController.hpp"
 #include "singletons/Toasts.hpp"
 #include "util/RapidJsonSerializeQString.hpp"
-#include "util/StreamerMode.hpp"
 #include "widgets/Notebook.hpp"
 
 #include <pajlada/settings/setting.hpp>
@@ -68,6 +67,12 @@ enum class ChatSendProtocol : int {
     Helix = 2,
 };
 
+enum StreamerModeSetting {
+    Disabled = 0,
+    Enabled = 1,
+    DetectStreamingSoftware = 2,
+};
+
 /// Settings which are availlable for reading and writing on the gui thread.
 // These settings are still accessed concurrently in the code but it is bad practice.
 class Settings