updating changelog for v3.12.0 release, [skip-ci]
updating changelog for v3.12.0 release, [skip-ci]

justinchu17/ilios,ilios/ilios,dartajax/ilios,thecoolestguy/ilios,stopfstedt/ilios,Trott/ilios,justinchu17/ilios,justinchu17/ilios,stopfstedt/ilios,dartajax/ilios,justinchu17/ilios,ilios/ilios,thecoolestguy/ilios,Trott/ilios