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/splits/SplitContainer.cpp

@@ -3,6 +3,7 @@
 #include "Application.hpp"
 #include "common/Common.hpp"
 #include "common/QLogging.hpp"
+#include "common/WindowDescriptors.hpp"
 #include "debug/AssertInGuiThread.hpp"
 #include "singletons/Fonts.hpp"
 #include "singletons/Theme.hpp"
@@ -15,7 +16,6 @@
 #include "widgets/splits/Split.hpp"
 #include "widgets/Window.hpp"
 
-#include <boost/foreach.hpp>
 #include <QApplication>
 #include <QJsonArray>
 #include <QJsonObject>