chore(gui): implement basic disassembler

Also implement CPU and Interrupt debug information.

Of note:
1. IE and IRQ status boxes are slightly misaligned
2. Whenever the disassembler accidentally reads into game data rather
   than executable code the emulator crashes
   * Thus I should turn Instruction decoding into a Result<> rather than
     panic on failure

src/main.rs

@@ -150,7 +150,7 @@ fn main() {
 
                 // Begin to draw Egui components
                 platform.begin_frame();
-                gui::draw_egui(&mut app, &platform.context(), texture_id);
+                gui::draw_egui(&cpu, &mut app, &platform.context(), texture_id);
                 // End the UI frame. We could now handle the output and draw the UI with the backend.
                 let (_, paint_commands) = platform.end_frame(Some(&window));
                 let paint_jobs = platform.context().tessellate(paint_commands);