Implement togggle events for Dialog show/showModal/close
This also slightly refactors FireToggleEvent to allow to to
accomodate both popovers and now also dialogs
Differential Revision: https://phabricator.services.mozilla.com/D225449
bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1876762
gecko-commit: a8b51403fa4f1dd6d936826f2a5b14c670426f3d
gecko-reviewers: smaug