Forward declare some things to speed up compile (#6162)

* Forward declare NativeMessagingServer and use a unique_ptr

* Forward declare GenericListModel to save on unneeded includes of its
header

src/controllers/completion/sources/CommandSource.cpp

@@ -5,6 +5,7 @@
 #include "controllers/commands/CommandController.hpp"
 #include "controllers/completion/sources/Helpers.hpp"
 #include "providers/twitch/TwitchCommon.hpp"
+#include "widgets/splits/InputCompletionItem.hpp"
 
 namespace chatterino::completion {
 

src/controllers/completion/sources/EmoteSource.cpp

@@ -11,6 +11,7 @@
 #include "providers/twitch/TwitchChannel.hpp"
 #include "providers/twitch/TwitchIrcServer.hpp"
 #include "singletons/Emotes.hpp"
+#include "widgets/splits/InputCompletionItem.hpp"
 
 namespace chatterino::completion {
 

src/controllers/completion/sources/Source.hpp

@@ -1,13 +1,10 @@
 #pragma once
 
-#include "widgets/listview/GenericListModel.hpp"
-#include "widgets/splits/InputCompletionItem.hpp"
-
 #include <QStringList>
 
-#include <memory>
-#include <utility>
-#include <vector>
+namespace chatterino {
+class GenericListModel;
+}  // namespace chatterino
 
 namespace chatterino::completion {
 

src/controllers/completion/sources/UnifiedSource.cpp

@@ -1,5 +1,7 @@
 #include "controllers/completion/sources/UnifiedSource.hpp"
 
+#include "widgets/listview/GenericListModel.hpp"
+
 namespace chatterino::completion {
 
 UnifiedSource::UnifiedSource(std::vector<std::unique_ptr<Source>> sources)

src/controllers/completion/sources/UserSource.cpp

@@ -4,6 +4,7 @@
 #include "providers/twitch/TwitchChannel.hpp"
 #include "singletons/Settings.hpp"
 #include "util/Helpers.hpp"
+#include "widgets/splits/InputCompletionItem.hpp"
 
 namespace chatterino::completion {