WIP: egl/wayland: dmabuf-hints

This add support for dmabuf-hints. See wayland/wayland-protocols!8 (merged)

This is marked as WIP because dmabuf-hints has not been merged upstream yet, and currently to help discussions for the protocol. It's based on a change where primary_device is a PATH_ID_TAG string rather than a file descriptor; this may change. See wayland/wayland-protocols#10 (closed).
It also needs a bit more testing with a real compositor implementation sending dynamic surface hints.

When the compositor sends new hints for a surface, we will reallocate buffers based them.

This makes wl_drm an optional protocol to be advertised by the compositor, as now zwp_linux_dmabuf_v1 can give us the device to use.