Refactor ROM handling and remove SharedRom singleton for improved architecture

- Eliminated the SharedRom class to enhance modularity and reduce global state management.
- Updated various classes to directly manage ROM instances, improving clarity and encapsulation.
- Added new functions for loading messages and colors from ROM, enhancing functionality.
- Refactored Canvas and Editor classes to utilize direct ROM references, streamlining interactions.
- Improved documentation and comments for better code understanding and maintainability.

src/app/emu/video/ppu.h

@@ -250,7 +250,7 @@ struct BackgroundLayer {
   bool enabled;                     // Whether the background layer is enabled
 };
 
-class Ppu : public SharedRom {
+class Ppu {
  public:
   // Initializes the PPU with the necessary resources and dependencies
   Ppu(Memory& memory) : memory_(memory) {}