Fixes T4136.
When listing projects in the "Visible To" selector control:
- Instead of showing every project you are a member of, show only a few.
- Add an option to choose something else which isn't in the menu.
- If you've used the control before, show the stuff you've selected in the recent past.
- If you haven't used the control before or haven't used it much, show the stuff you've picked and them some filler.
- Don't offer milestones.
- Also don't offer milestones in the custom policy UI.
