Move an epic to another group via quick action

Problem to solve

Sometimes the scope of an epic changes and is either narrower (only affecting a subgroup) or wider (affecting sibling groups / the parent group) afterwards. The current workflow for those cases is to create a new epic and copy all issues individually, which leads to a poor user experience.

Proposal

We should support moving epics to other groups like we do for issues. As a first iteration of this, we should support moving epics via the /move quick action.