Add a lev and tal role, and one role per year so relevant permissions can be managed in one go

- [ ] Add a lev role and a tal role
- [ ] Add a role for each existing year
- [ ] Assign all current students to lev or tal, and to one of the year roles
- [ ] Make the bot auto-assign new students to these new roles as well
- [ ] Bot no longer needs to add new year's roles to each campus chat
- [ ] Change each year's co-ed channel to use the year role instead of both class roles
- [ ] Make bot use the year role instead of both class roles when creating new year channels