refactor: extract common code in mod pages and model

This creates a hierarchy in which ModPage and ModModel are the parents
of every mod provider, providing the basic functionality common to all
of them.

It also imposes a unique .ui file (they were already equal before, just
duplicated basically) on all mod providers.

launcher/ui/pages/modplatform/ModModel.h

@@ -0,0 +1,60 @@
+#pragma once
+
+#include <QAbstractListModel>
+
+#include "modplatform/ModIndex.h"
+#include "net/NetJob.h"
+
+class ModPage;
+
+namespace ModPlatform {
+
+typedef QMap<QString, QIcon> LogoMap;
+typedef std::function<void(QString)> LogoCallback;
+
+class ListModel : public QAbstractListModel {
+    Q_OBJECT
+
+   public:
+    ListModel(ModPage* parent);
+    virtual ~ListModel();
+
+    int rowCount(const QModelIndex& parent) const override;
+    int columnCount(const QModelIndex& parent) const override;
+    QVariant data(const QModelIndex& index, int role) const override;
+    Qt::ItemFlags flags(const QModelIndex& index) const override;
+    bool canFetchMore(const QModelIndex& parent) const override;
+    void fetchMore(const QModelIndex& parent) override;
+
+    void getLogo(const QString& logo, const QString& logoUrl, LogoCallback callback);
+    void searchWithTerm(const QString& term, const int sort);
+
+   protected slots:
+    virtual void performPaginatedSearch() = 0;
+    virtual void searchRequestFinished() = 0;
+
+    void logoFailed(QString logo);
+    void logoLoaded(QString logo, QIcon out);
+
+    void searchRequestFailed(QString reason);
+
+   protected:
+    void requestLogo(QString file, QString url);
+
+   protected:
+    ModPage* m_parent;
+
+    QList<ModPlatform::IndexedPack> modpacks;
+    QStringList m_failedLogos;
+    QStringList m_loadingLogos;
+    LogoMap m_logoMap;
+    QMap<QString, LogoCallback> waitingCallbacks;
+
+    QString currentSearchTerm;
+    int currentSort = 0;
+    int nextSearchOffset = 0;
+    enum SearchState { None, CanPossiblyFetchMore, ResetRequested, Finished } searchState = None;
+    NetJob::Ptr jobPtr;
+    QByteArray response;
+};
+}  // namespace ModPlatform