protocol: add wl_output.{name,description}

This is inspired from xdg-output-unstable-v1. This allows clients to
get the name and description without having to use xdg_output. This
should eventually allow us to restrict xdg_output to clients like
Xwayland.

The name is a unique non-persistent user-friendly string that can be
used to refer to an output. This can be used by Wayland clients to
refer to a specific wl_output (e.g. across processes or in CLI
arguments).

The description is a non-unique user-friendly string that can be
displayed to the user.

Signed-off-by: Simon Ser <contact@emersion.fr>
References: https://gitlab.freedesktop.org/wayland/wayland-protocols/-/issues/7