refactor: move url creation for mods to modplatform/

Moves all things related to creating the URLs of the mod platforms
that go to network tasks to a single place, so that:

1. Maintaining and fixing eventual issues is more straightforward.
2. Makes it possible to factor out more common code between the
   different modplatform pages

launcher/ui/pages/modplatform/flame/FlameModModel.h

@@ -30,8 +30,10 @@ class ListModel : public ModPlatform::ListModel {
     virtual ~ListModel();
 
    private slots:
-    void performPaginatedSearch() override;
     void searchRequestFinished() override;
+
+   private:
+    const char** getSorts() const override;
 };
 
 }  // namespace Modrinth