ControllerInterface/Xlib: Combine keycodes with the same name to fix non-working inputs.

[jordan-woyak]

This issue was just reported on discord.

Apparently multiple keycodes can have the same keysym and thus the same name. Our input system will bind to the first matching name so some keyboard keys could end up not working.

I've made the Key class hold a vector of these overlapping keycodes. An alternative fix would require giving these keycodes unique input names.

I suppose in the future we could expose both the current "pretty" name and the keycode as the name itself, but I think this is a good enough fix for now.

This might fix https://bugs.dolphin-emu.org/issues/13784