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/minecraft/mod/ShaderPackFolderModel.h

@@ -0,0 +1,10 @@
+#pragma once
+
+#include "ResourceFolderModel.h"
+
+class ShaderPackFolderModel : public ResourceFolderModel {
+    Q_OBJECT
+
+   public:
+    explicit ShaderPackFolderModel(const QString& dir) : ResourceFolderModel(QDir(dir)) {}
+};