color: add wp_image_description_v1.done and target_primaries
The get_information
request talks about 'done' event, but it didn't
actually exist, so let's add it.
target_primaries
event mirrors set_mastering_display_primaries
, delivering
similar information in the opposite direction. This allows clients to target a suitable color
sub-volume and avoid gamut mapping in the compositor, particularly for
HDR-like use cases.
The old primaries are renamed to container primaries to reduce confusion.