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/widgets/settingspages/GeneralPageView.cpp

@@ -1,7 +1,6 @@
 #include "widgets/settingspages/GeneralPageView.hpp"
 
 #include "Application.hpp"
-#include "singletons/WindowManager.hpp"
 #include "util/LayoutHelper.hpp"
 #include "util/RapidJsonSerializeQString.hpp"
 #include "widgets/dialogs/ColorPickerDialog.hpp"
@@ -9,6 +8,7 @@
 #include "widgets/helper/Line.hpp"
 
 #include <QRegularExpression>
+#include <QScrollArea>
 #include <QScrollBar>
 
 namespace {