qapi: Plug trivial documentation holes around former simple unions
The conversion of simple to flat unions left the @data members
undocumented. Add documentation where it's trivial. Copy verbatim
from the wrapped type's description where possible.
Leftovers: String (to be taken care of in the next commit), and
TransActionAction (left for another day).
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <
20240205074709.
3613229-13-armbru@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>