feat: add ConcurrentTask

This tasks (or rather, meta-task) has the ability to run several other
sub tasks concurrently.

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

launcher/tasks/ConcurrentTask.h

@@ -0,0 +1,58 @@
+#pragma once
+
+#include <QQueue>
+#include <QSet>
+
+#include "tasks/Task.h"
+
+class ConcurrentTask : public Task {
+    Q_OBJECT
+public:
+    explicit ConcurrentTask(QObject* parent = nullptr, QString task_name = "", int max_concurrent = 6);
+    virtual ~ConcurrentTask();
+
+    inline auto isMultiStep() const -> bool override { return m_queue.size() > 1; };
+    auto getStepProgress() const -> qint64 override;
+    auto getStepTotalProgress() const -> qint64 override;
+
+    inline auto getStepStatus() const -> QString override { return m_step_status; }
+
+    void addTask(Task::Ptr task);
+
+public slots:
+    bool abort() override;
+
+protected
+slots:
+    void executeTask() override;
+
+    virtual void startNext();
+
+    void subTaskSucceeded(Task::Ptr);
+    void subTaskFailed(Task::Ptr, const QString &msg);
+    void subTaskStatus(const QString &msg);
+    void subTaskProgress(qint64 current, qint64 total);
+
+protected:
+    void setStepStatus(QString status) { m_step_status = status; emit stepStatus(status); };
+
+    virtual void updateState();
+
+protected:
+    QString m_name;
+    QString m_step_status;
+
+    QQueue<Task::Ptr> m_queue;
+
+    QHash<Task*, Task::Ptr> m_doing;
+    QHash<Task*, Task::Ptr> m_done;
+    QHash<Task*, Task::Ptr> m_failed;
+
+    int m_total_max_size;
+    int m_total_size;
+
+    qint64 m_stepProgress = 0;
+    qint64 m_stepTotalProgress = 100;
+
+    bool m_aborted = false;
+};