feat: Identify modifiers on Wayland/X11 (new)

[gabyx]

Fixes: #4626

• This implementation is the first modifier detection client-side workaround as Kitty does for Wayland.
• For X11 the code checks the modifier table and tries to match a single virtual modifiers to a single real modifier (ctrl, shift, capslock, mod1...mod5).
• On Wayland the workaround goes by probing the keyboard for all keys and rebuilding the missing API which is not available as in X11.

The solution is encapsulated out in file modifiers.rs for both X11 and Wayland.

• I am sure about how to test this, since it uses xkb and its state...
• @wez: A review is appreciated to let me know if we should go on with this, or there is any better idea from your side.
  This PR contains the port of Kittys C code for Wayland.