docs/qapidoc: process @foo into ``foo``

docs/qapidoc: process @foo into ``foo``

Add support for the special QAPI doc syntax to process @references as
``preformatted text``. At the moment, there are no actual
cross-references for individual members, so there is nothing to link
against. For now, process it identically to how we did in the old
qapidoc system.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-ID: <20250311034303.75779-56-jsnow@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>