ui/console: declare console types in console.h

We are going to split the console.c unit next, and implement
separately. But we need to check the underlying type in various places.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20230830093843.3531473-36-marcandre.lureau@redhat.com>