native surface: Add scanout handlers

native surface: Add scanout handlers

When a native surface ends up on a hardware plane, the caller needs to
know about it so it can prevent the resource from being destroyed while
on scanout (which may cause an implicit page flip and a stall), and
so it knows that the content may have changed usage domains.

This adds stubs for dealing with this - only for wl dmabuf right now, but
it may be useful for other surface types later.