refactor: adapt rest of the codebase to the new resource model

In order to access the ModFolderModel from the ModFolderPage, i created
a new m_model for the correct type, shadowing the m_model of type
ResourceFolderModel. This creates two shared_ptr references to the same object,
but since they will have the same lifetime, it doesn't generate a memory
leak.

Signed-off-by: flow <flowlnlnln@gmail.com>

launcher/ui/pages/instance/ModFolderPage.h

@@ -55,9 +55,20 @@ class ModFolderPage : public ExternalResourcesPage {
     virtual bool shouldDisplay() const override;
     void runningStateChanged(bool running) override;
 
+   public slots:
+    bool onSelectionChanged(const QModelIndex& current, const QModelIndex& previous) override;
+
+    void itemActivated(const QModelIndex& index) override;
+
+    void enableItem() override;
+    void disableItem() override;
+
    private slots:
     void installMods();
     void updateMods();
+
+   protected:
+    std::shared_ptr<ModFolderModel> m_model;
 };
 
 class CoreModFolderPage : public ModFolderPage {