Refactor flag handling: move FlagParser implementation to flag.cc, remove ResourceManager, and update includes

src/app/editor/system/resource_manager.h

@@ -1,28 +0,0 @@
-#ifndef YAZE_APP_EDITOR_SYSTEM_RESOURCE_MANAGER_H
-#define YAZE_APP_EDITOR_SYSTEM_RESOURCE_MANAGER_H
-
-#include <cstddef>
-
-namespace yaze {
-namespace editor {
-
-// System resource manager.
-class ResourceManager {
- public:
-  ResourceManager() : count_(0) {}
-  ~ResourceManager() = default;
-
-  void Load(const char* path);
-  void Unload(const char* path);
-  void UnloadAll();
-
-  size_t Count() const;
-
- private:
-  size_t count_;
-};
-
-} // namespace editor
-} // namespace yaze
-
-#endif // YAZE_APP_EDITOR_SYSTEM_RESOURCE_MANAGER_H