refactor: move general code from mod model to its own model

This aims to continue decoupling other types of resources (e.g. resource
packs, shader packs, etc) from mods, so that we don't have to
continuously watch our backs for changes to one of them affecting the
others.

To do so, this creates a more general list model for resources, based on
the mods one, that allows you to extend it with functionality for other
resources.

I had to do some template and preprocessor stuff to get around the
QObject limitation of not allowing templated classes, so that's sadge :c

On the other hand, I tried cleaning up most general-purpose code in the
mod model, and added some documentation, because it looks nice :D

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

launcher/minecraft/mod/tasks/BasicFolderLoadTask.h

@@ -0,0 +1,44 @@
+#pragma once
+
+#include <QDir>
+#include <QMap>
+#include <QObject>
+
+#include <memory>
+
+#include "minecraft/mod/Resource.h"
+
+#include "tasks/Task.h"
+
+/** Very simple task that just loads a folder's contents directly. 
+ */
+class BasicFolderLoadTask : public Task
+{
+    Q_OBJECT
+public:
+    struct Result {
+        QMap<QString, Resource::Ptr> resources;
+    };
+    using ResultPtr = std::shared_ptr<Result>;
+
+    [[nodiscard]] ResultPtr result() const {
+        return m_result;
+    }
+
+public:
+    BasicFolderLoadTask(QDir dir) : Task(nullptr, false), m_dir(dir), m_result(new Result) {}
+    void executeTask() override
+    {
+        m_dir.refresh();
+        for (auto entry : m_dir.entryInfoList()) {
+            auto resource = new Resource(entry);
+            m_result->resources.insert(resource->internal_id(), resource);
+        }
+
+        emitSucceeded();
+    }
+
+private:
+    QDir m_dir;
+    ResultPtr m_result;
+};