Make wayland load cursors on demand

Add and use a modified libwayland-cursor in-tree,
just as done in the main branch for GTK4

gdk/wayland/meson.build

@@ -1,3 +1,5 @@
+subdir('cursor')
+
 gdk_wayland_sources = files(
   'gdkapplaunchcontext-wayland.c',
   'gdkcursor-wayland.c',
@@ -31,7 +33,6 @@ gdk_wayland_deps = [
   xkbdep,
   wlclientdep,
   wlprotocolsdep,
-  wlcursordep,
   wlegldep,
 ]
 
@@ -112,4 +113,5 @@ libgdk_wayland = static_library('gdk-wayland',
                                   '-DG_LOG_DOMAIN="Gdk"',
                                 ] + common_cflags,
                                 link_args: common_ldflags,
+                                link_with: [libwayland_cursor, ],
                                 dependencies: [ gdk_deps, gdk_wayland_deps, ])