Allow stacked comment actions to be explicitly ordered
Ref T6027. Normally, actions use the same order as the form, but in some cases (like moving stuff on workboards) it makes sense to reorder them explicitly.
Pin "Move on board" near the bottom, and "projects/subscribers" at the bottom. I think these are generally reasonable rules in all cases.
Test Plan: Opened menu, saw slightly better action order.
Reviewed By: chad
Maniphest Tasks: T6027
Differential Revision: https://secure.phabricator.com/D15639