Add message preview functionality and refactor MessageEditor

- Introduced MessagePreview class to handle message rendering and preview logic.
- Updated MessageEditor to utilize MessagePreview for drawing messages and managing font graphics.
- Refactored drawing methods to improve organization and clarity, including the addition of DrawFontAtlas and DrawExpandedMessageSettings.
- Enhanced message handling by integrating new dictionary entry lookup and improved bitmap updates for message previews.
- Cleaned up unused functions and variables to streamline the codebase.

src/app/editor/editor.cmake

@@ -7,6 +7,7 @@ set(
   app/editor/music/music_editor.cc
   app/editor/message/message_editor.cc
   app/editor/message/message_data.cc
+  app/editor/message/message_preview.cc
   app/editor/code/assembly_editor.cc
   app/editor/graphics/screen_editor.cc
   app/editor/graphics/graphics_editor.cc