control_menu: Move processing and display code into it's correspondind methods

includes/control_menu.hpp

@@ -9,6 +9,7 @@
 #pragma once
 
 #include <context.hpp>
+#include <types.hpp>
 
 namespace gol {
 
@@ -21,6 +22,7 @@ public:
 private:
   ctx context_;
 public: // Keep those public for easy access
+  MenuState menu_state_ = MenuState::NONE;
   int fps_ctrl_ = false;
   int cell_size_ctrl_ = false;
   bool play_ctrl_ = true;