How best to handle Event Dispatchers during upgrade
As shown by #1449 (closed) and in PRs https://github.com/civicrm/civicrm-core/pull/13551 and https://github.com/civicrm/civicrm-core/pull/16034 there have been shown issues with dispatching most hooks when in upgrade mode, this ticket is to discuss the best ways forward and if we need to move the whitelisting or similar to the dispatcher or elsewhere ping @eileen @totten