Cleanup and unify keyboard input.

- Unify keycode values (secondary label printed on a key), remove unused hardcoded Latin-1 codes.
- Unify IME behaviour, add inline composition string display on Windows and X11.
- Add key_label (localized label printed on a key) value to the key events, and allow mapping actions to the unshifted Unicode events.
- Add support for physical keyboard (Bluetooth or Sidecar) handling on iOS.
- Add support for media key handling on macOS.

Co-authored-by: Raul Santos <raulsntos@gmail.com>

platform/linuxbsd/detect.py

@@ -192,6 +192,7 @@ def configure(env: "Environment"):
         env.ParseConfig("pkg-config xrandr --cflags")
         env.ParseConfig("pkg-config xrender --cflags")
         env.ParseConfig("pkg-config xi --cflags")
+        env.ParseConfig("pkg-config xkbcommon --cflags")
 
     if env["touch"]:
         env.Append(CPPDEFINES=["TOUCH_ENABLED"])