cpu_manager: Add missing includes

Previously this header was relying on indirect inclusions that are no
longer satisfied.

src/core/cpu_manager.h

@@ -9,6 +9,9 @@
 #include <functional>
 #include <memory>
 #include <thread>
+
+#include "common/fiber.h"
+#include "common/thread.h"
 #include "core/hardware_properties.h"
 
 namespace Common {