Refactor graphics sheet management with singleton class

Refactor the handling of graphics sheets by introducing a singleton class `GraphicsSheetManager`. This centralizes the management of graphics sheets, replacing direct access through the `Rom` object. Key changes include:

- Updated various methods across multiple classes to use `GraphicsSheetManager::GetInstance()` for accessing and manipulating graphics sheets.
- Introduced standalone functions `LoadLinkGraphics`, `LoadAllGraphicsData`, and `SaveAllGraphicsData` for loading and saving graphics data.
- Refactored the `Rom` class to remove methods and member variables related to graphics sheet management.
- Updated `OverworldEditor` to use `std::array` for `maps_bmp_` and added error handling for `std::bad_alloc` exceptions.
- Improved code modularity and error handling throughout the application.

src/app/editor/editor_manager.cc

@@ -64,7 +64,9 @@ absl::Status EditorManager::Update() {
   DrawInfoPopup();
 
   if (rom()->is_loaded() && !rom_assets_loaded_) {
-    RETURN_IF_ERROR(rom()->LoadAllGraphicsData())
+		auto& sheet_manager = GraphicsSheetManager::GetInstance();
+    ASSIGN_OR_RETURN(*sheet_manager.mutable_gfx_sheets(),
+                     LoadAllGraphicsData(*rom()))
     RETURN_IF_ERROR(overworld_editor_.LoadGraphics());
     rom_assets_loaded_ = true;
   }
@@ -691,6 +693,10 @@ void EditorManager::SaveRom() {
   status_ = overworld_editor_.Save();
   RETURN_VOID_IF_ERROR(status_);
 
+  if (core::ExperimentFlags::get().kSaveGraphicsSheet)
+    PRINT_IF_ERROR(SaveAllGraphicsData(*rom(), 
+      GraphicsSheetManager::GetInstance().gfx_sheets()));
+
   status_ = rom()->SaveToFile(backup_rom_, save_new_auto_);
 }