Ref T10010.
- Default name to "Milestone X".
- Remove policy controls, which have no effect.
- Don't generate slugs for milestones since this is a big pain where they all generate as #milestone_1 by default (you can add one if you want). I plan to add some kind of syntax like #parent/32 to mean "Milestone 32 in Parent" later.
- Don't require projects to have unique names (again, 900 copies of "Milestone X"). I think we can trust users to sort this out for themselves since modern Phabricator has "Can Create Projects" permission, etc.