Ref T4103. A few bits here:

• We have an ancient "tiles" preference which was just a fallback from 2-3 years ago. Throw that away.
• Modenize the other pinned stuff. We should likely revisit this after the next homepage update but I just left the actual defaults alone for now.
• Lightly prepare for global default editing.
• Add a "reset to defaults" option.

• Pinned, unpinned, reordered and reset application homepage order.