refactor(RD): decouple ResourceModels from ResourcePages

This makes it so that we don't need a reference to the parent page in
the model. It will be useful once we change the page from a widget-based
one to a QML page.

It also makes tasks be created in the dialog instead of the page, so
that the dialog can also have the necessary information to mark versions
as selected / deselected easily. It also makes the task pointers into
smart pointers.

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

launcher/ui/pages/modplatform/modrinth/ModrinthResourcePages.cpp

@@ -47,7 +47,7 @@ namespace ResourceDownload {
 ModrinthModPage::ModrinthModPage(ModDownloadDialog* dialog, BaseInstance& instance)
     : ModPage(dialog, instance)
 {
-    m_model = new ModrinthModModel(this);
+    m_model = new ModrinthModModel(instance);
     m_ui->packView->setModel(m_model);
 
     // index is used to set the sorting with the modrinth api