refactor: Enhance MusicEditor functionality and UI components

- Updated the `MusicEditor` class to integrate a new playback engine (`emu::Apu`) for real-time music playback.
- Refactored UI components to improve the music editing experience, including dynamic song selection and enhanced visualization of music data.
- Introduced methods for starting and stopping playback, along with a new tracker view for displaying song patterns and commands.
- Removed obsolete methods and streamlined the drawing functions for better maintainability and clarity.
- Added detailed implementation plans as comments to guide future development and feature integration.

src/app/zelda3/music/tracker.h

@@ -222,6 +222,10 @@ class Tracker {
   SongRange *song_range_;
   SpcCommand *current_spc_command_;
 
+  const SpcCommand& GetSpcCommand(short index) const {
+    return current_spc_command_[index];
+  }
+
   SongSpcBlock **ssblt;
 
   ZeldaWave *waves;