wayland/surface: Use wl_surface_offset() instead of x,y of attach()

wayland/surface: Use wl_surface_offset() instead of x,y of attach()

This makes the hotspot of DND surfaces work when using the Vulkan and
OpenGL renderers.

This bumps the CI image used to the newly built image. This is needed to
install a new enough libwayland-client.so needed for wl_surface.offset.

This is done by adding wayland as a meson subproject, building it
on-demand if the version in the system is not new enough. As
libwayland-client.so is pulled in implicitly when linking to gtk4, the
compile step needs LD_LIBRARY_PATH set to make ld find the right library
to link to.