On X11, use events modifiers to detect state

While there's a separate event to deliver modifiers for keyboard,
unfortunately, it's not even remotely reflects the modifiers state.

Thus use events along side regular modifier updates to correctly
detect the state. Also, apply the modifiers from the regular
key event by converting their state to xkb modifiers state.

Links: https://github.com/alacritty/alacritty/issues/7549
Closes: #3388

src/platform_impl/linux/common/mod.rs

@@ -1,2 +1 @@
-pub mod keymap;
-pub mod xkb_state;
+pub mod xkb;