Add RenderRoomGraphics method to Room class for improved graphics rendering

Implement RenderRoomGraphics in the Room class to handle the rendering of room graphics, including floor and background drawing. This addition enhances the graphics management by utilizing the gfx::Arena for rendering operations and updating bitmaps as needed. Update room.h to declare the new method.

src/app/zelda3/dungeon/room.h

@@ -204,6 +204,7 @@ class Room {
 
   void LoadRoomGraphics(uint8_t entrance_blockset = 0xFF);
   void CopyRoomGraphicsToBuffer();
+  void RenderRoomGraphics();
   void LoadAnimatedGraphics();
   void LoadObjects();
   void LoadSprites();