R1:d182d7eaf1d1

Remove menu item pinning from Home and Favorites profile menus

Summary:
Ref T12174.

- Home now always uses the topmost item (falling back to "magic home") and no longer supports pinning. If any personal item may be a default item, it will always be picked over any global item.
- Favorites doesn't use defaults anyway, but no longer has misleading UI suggesting it might.

Test Plan:
- Saw no pinning UI on Home/Favorites.
- Added a personal dashboard on Home, it automatically became the new default.