Bring back the SU AGM

Extra Information: Unless you run and get elected in one of the SU committees/conferences it is imposssible to attend higher level SU meetings. Therefore "normal" students cannot vote on policy, unless going through a very confusing online system that nobody knows about, or hold officers easily to account. We should bring back the AGM/SUM to give everyone a fair chance to be involved in the democratic procedures of the SU alongside the current student council so there is good representation across the student body.