Add Arrange Icons to Icons menu

[midwan]

Summary

• Add an Icons -> Arrange Icons submenu using the existing by Name, by Type, by Size, and by Date arrange actions.
• Wire the same arrange command IDs through desktop, group, and lister menu handling.
• Add static regression coverage for the top Icons menu entries and dispatch paths.

Testing

• python3 -m unittest discover -s source/Program/tests
• git diff --check HEAD~1..HEAD