xwayland/glamor: make wl_drm optional
This MR adds zwp_linux_dmabuf_feedback_v1 support and makes wl_drm optional. The motivation is that Chrome EXO (a wayland compositor) does not support wl_drm, and it seems zwp_linux_dmabuf_feedback_v1 can obsolete wl_drm.
I am not super familiar with either xwayland or the wayland protocols. Adding folks that I think can help.