R1:51ed95c00b8d

Give profile menus more straightforward hide/disable/delete/default interactions

Summary:
Ref T10054.

- Just let users delete non-builtin items.
- Let users choose a default item explicitly.
- Do a better job of cleaning up items which no longer exist or belong to uninstalled applications.

(NOTE) This has one user-facing change: workboards are no longer the default on projects with workboards. I think this is probably OK since we're giving users a ton of new toys at the same time, but I'll write…