Remove Unnecessary Includes in Headers (#4275)

* refactor: remove unnecessary includes in headers

* fix: formatting

* chore: changelog

* fix: scrollbar

* fix: suggestions and old appbase remains

* fix: suggestion

* fix: missing Qt forward declarations

* fix: another qt include

* fix: includes for precompiled-headers=off

* Add missing `<memory>` includes

* Add missing `#pragma once`

* Fix tests

Co-authored-by: Rasmus Karlsson <rasmus.karlsson@pajlada.com>

src/Application.hpp

@@ -1,6 +1,5 @@
 #pragma once
 
-#include "common/SignalVector.hpp"
 #include "common/Singleton.hpp"
 #include "singletons/NativeMessaging.hpp"
 
@@ -25,7 +24,6 @@ class Theme;
 class WindowManager;
 class Logging;
 class Paths;
-class AccountManager;
 class Emotes;
 class IEmotes;
 class Settings;