vulkan/wsi: Only use a single fd per wsi_image

vulkan/wsi: Only use a single fd per wsi_image

The only thing this was helping was X11 where the protocol requires that
we pass in an array of images.  We can move all the dup() code to the
X11 back-end and leave the others a bit cleaner.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Simon Ser <contact@emersion.fr>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16333>