[Zion] Add a proc/thread cleanup thread for future use.

zion/scheduler/cleanup.h

@@ -0,0 +1,25 @@
+#pragma once
+
+#include <glacier/container/linked_list.h>
+#include <glacier/memory/ref_ptr.h>
+
+#include "object/process.h"
+#include "object/semaphore.h"
+#include "object/thread.h"
+
+class ProcessCleanup {
+ public:
+  ProcessCleanup() {}
+
+  void CleanupLoop();
+
+  void CleanupProcess(glcr::RefPtr<Process> process);
+  void CleanupThread(glcr::RefPtr<Thread> thread);
+
+ private:
+  Semaphore semaphore_;
+  glcr::LinkedList<glcr::RefPtr<Thread>> thread_list_;
+  glcr::LinkedList<glcr::RefPtr<Process>> process_list_;
+};
+
+void CleanupThreadEntry(ProcessCleanup* cleanup);