Add support for cleaning old aerial wallpaper videos in:
/Users/user/Library/Application Support/com.apple.wallpaper/aerials/videos
These video files can consume significant disk space (up to 50GB+) and
are safe to remove - macOS will re-download them on demand.
Uses MOLE_SUPPORT_CACHE_AGE_DAYS (default 30 days) to avoid removing
recently used wallpapers.
Closes#508
922f5f1fc9