win32: precalculate keymap at display opening

The default keymap and keymap layouts are calculated on request.
If done once a surface is setup and listening at win32 events,
we may then enter in a recursive loop.
To avoid this, precalculate the keymap as soon as displays are open.

Fixes #6203
Closes #6203

gdk/win32/gdkdisplay-win32.c

@@ -548,6 +548,9 @@ _gdk_win32_display_open (const char *display_name)
 
   g_signal_emit_by_name (_gdk_display, "opened");
 
+  /* Precalculate keymap, see #6203 */
+  (void) _gdk_win32_display_get_keymap (_gdk_display);
+
   GDK_NOTE (MISC, g_print ("... _gdk_display now set up\n"));
 
   return _gdk_display;