Add option for separate configuration of in-game and menu controls

[nightmareci]

I think this option should only be available for non-controller input types (joystick, keyboard, Linux GPIO). Controllers should use a fixed layout for menu controls, with configuration only affecting in-game controls.

The separately-configurable functionality should be made available with an on/off option, off by default. When off, one mapping is used for both game and menu controls, working the same way as the game currently works. When switched on, game and menu controls become separately configurable, the two configurations defaulting to the layout used when the enable-option was off. When switched off, the configuration defaults to the previous menu input layout, because the player is already in the menu, so menu input continues to work "as expected".