gdk: Add properties in GdkEventKey for the constructor

IBus GTK4 IM module needs to modify the state of GdkEventKey during
the async filter_keypress(). Since GTK4 GdkEventKey is an object,
the IM module retrieves all the member of GdkEventKey and can create
a new GdkEventKey with the updated state in this way.

Fix GNOME/gtk!1208
4 jobs for gdkevent-set-state in 20 minutes and 21 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Build
passed #160562
fedora-x86_64

00:03:57

passed #160563
win32
msys2-mingw32

00:14:15

 
  Flatpak
passed #160564
flatpak:demo

00:06:02

passed #160565
flatpak:widget-factory

00:06:04