refactor: move NetJob away from ModModel to ModAPI

This is done so that 1. ModAPI behaves more like an actual API instead
of just a helper, and 2. Allows for more easily creating other mod
providers that may or may not use network tasks (foreshadowing lol)

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

@@ -22,5 +22,5 @@ class FlameModPage : public ModPage {
     bool shouldDisplay() const override;
 
    private:
-    void onRequestVersionsSucceeded(ModPage*, QByteArray*, QString) override;
+    void onRequestVersionsSucceeded(QJsonDocument&, QString) override;
 };