fix: properly intialize key event in GlobalEventTap (#7462)

Fixes #7215. The issue was that `GlobalEventTap` didn't fully initialize
the key event before passing it to `ghostty_app_key`. In particular, it
didn't set the `unshifted_codepoint` field, which is needed to find a
match when calling `keybind.set.getEvent`, because `keybind.set` stores
bindings by codepoint, not physical key (i.e., the trigger to match is
`ctrl+p`, not `ctrl+key_p`, et cetera).

The fix was to make `GlobalEventTap` initialize the key event using
`event.ghosttyKeyEvent`, like it's done in `SurfaceView.keyAction` and
`AppDelegate.localEventKeyDown`.

This is my first time touching either Zig or Swift, so I'm a bit green.
In particular, I don't know if it's possible to write a test covering
this, and if so, how and where to put it. Please edit or request changes
as you see fit.

macos/Sources/Features/Global Keybinds/GlobalEventTap.swift

@@ -141,12 +141,7 @@ fileprivate func cgEventFlagsChangedHandler(
     guard let event: NSEvent = .init(cgEvent: cgEvent) else { return result }
 
     // Build our event input and call ghostty
-    var key_ev = ghostty_input_key_s()
-    key_ev.action = GHOSTTY_ACTION_PRESS
-    key_ev.mods = Ghostty.ghosttyMods(event.modifierFlags)
-    key_ev.keycode = UInt32(event.keyCode)
-    key_ev.text = nil
-    key_ev.composing = false
+    var key_ev = event.ghosttyKeyEvent(GHOSTTY_ACTION_PRESS)
     if (ghostty_app_key(ghostty, key_ev)) {
         GlobalEventTap.logger.info("global key event handled event=\(event)")
         return nil