Add a ProcessManager class to store Process objects.

Trying out a new method for exposing global objects directly via a
variable.

zion/scheduler/process_manager.h

@@ -0,0 +1,23 @@
+#pragma once
+
+#include "lib/linked_list.h"
+#include "lib/shared_ptr.h"
+#include "scheduler/process.h"
+
+class ProcessManager {
+ public:
+  // Initializes the ProcessManager
+  // and stores it in the global variable.
+  static void Init();
+
+  void InsertProcess(const SharedPtr<Process>& proc);
+  Process& FromId(uint64_t id);
+
+  void DumpProcessStates();
+
+ private:
+  // TODO: This should be a hashmap.
+  LinkedList<SharedPtr<Process>> proc_list_;
+};
+
+extern ProcessManager* gProcMan;