This gives applications and binding systems a clearer view of what the hardware is so they can make intelligent decisions about how to present things to the user.
Gamepad mappings continue to use abxy for the face buttons for simplicity and compatibility with earlier versions of SDL, however the "SDL_GAMECONTROLLER_USE_BUTTON_LABELS" hint no longer has any effect.
Fixes https://github.com/libsdl-org/SDL/issues/6117
Also renamed most cases of SDL_GAMEPAD_TYPE_UNKNOWN to SDL_GAMEPAD_TYPE_STANDARD, and SDL_GetGamepadType() will return SDL_GAMEPAD_TYPE_UNKNOWN only if the gamepad is invalid.