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/common/ChannelChatters.hpp

@@ -1,15 +1,18 @@
 #pragma once
 
-#include "common/Channel.hpp"
 #include "common/ChatterSet.hpp"
 #include "common/UniqueAccess.hpp"
 #include "lrucache/lrucache.hpp"
 #include "util/QStringHash.hpp"
 
+#include <QColor>
+#include <QObject>
 #include <QRgb>
 
 namespace chatterino {
 
+class Channel;
+
 class ChannelChatters
 {
 public: