Refactor old ContentLoadingManager into Content for simplicity

Source/Engine/Content/Loading/LoadingThread.h

@@ -0,0 +1,50 @@
+// Copyright (c) 2012-2024 Wojciech Figat. All rights reserved.
+
+#pragma once
+
+#include "Engine/Threading/IRunnable.h"
+
+/// <summary>
+/// Resources loading thread.
+/// </summary>
+class LoadingThread : public IRunnable
+{
+protected:
+    volatile int64 _exitFlag;
+    Thread* _thread;
+    int32 _totalTasksDoneCount;
+
+public:
+    LoadingThread();
+    ~LoadingThread();
+
+public:
+    /// <summary>
+    /// Set exit flag to true so thread must exit
+    /// </summary>
+    void NotifyExit();
+
+    /// <summary>
+    /// Stops the calling thread execution until the loading thread ends its execution.
+    /// </summary>
+    void Join();
+
+    /// <summary>
+    /// Starts thread execution.
+    /// </summary>
+    /// <param name="name">The thread name.</param>
+    /// <returns>True if cannot start, otherwise false</returns>
+    bool Start(const String& name);
+
+    /// <summary>
+    /// Runs the specified task.
+    /// </summary>
+    /// <param name="task">The task.</param>
+    void Run(class ContentLoadTask* task);
+
+public:
+    // [IRunnable]
+    String ToString() const override;
+    int32 Run() override;
+    void Exit() override;
+};