Switch logic of approval chain to disallow editing/deleting by approvers

[grassick]

Approvers should only be able to approve or reject when preventEditing is true on approval stage.

• [x] Add to schema of form
• [x] Create UI (use storybook)
• [x] Do not allow draft for existing draft, must use redraft
• [x] Disallow canDelete for approvers with this set
• [x] Ensure that canEdit is false for approvers with this set
• [x] Check logic everywhere that does editing/deleting
• [ ] Enforce non-editing/deleting on server

[grassick]

Will do last point as part of server enforcement