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/graphics/graphics_editor.h

@@ -176,6 +176,7 @@ class GraphicsEditor : public SharedRom, public Editor {
   gfx::Bitmap bin_bitmap_;
   gfx::Bitmap link_full_sheet_;
   std::array<gfx::Bitmap, kNumGfxSheets> gfx_sheets_;
+	std::array<gfx::Bitmap, kNumLinkSheets> link_sheets_;
 
   gfx::PaletteGroup col_file_palette_group_;
   gfx::SnesPalette z3_rom_palette_;