Establish some consistency with extension logging. Some extensions use another format:
display_alert "message" "${EXTENSION}" "info"
These were *not* adapted to this new schema.
- rootfs: rootfs-create: show a summary of the 20 biggest dirs, right before tarring the rootfs (for debugging)
- rootfs: rootfs-create: show usage of caches between first and second stages
- rootfs: rootfs-create: cleanup junk left by `debootstrap` after second stage
- rootfs: rootfs-create: _always_ clean apt stuff at the end
- rename `apt_purge_unneeded_packages()` to `apt_purge_unneeded_packages_and_clean_apt_caches()` for clarity
- image: `apt_purge_unneeded_packages_and_clean_apt_caches()`: warn if apt caches not empty; clean them off, always.
- host-utils: `local_apt_deb_cache_prepare()`: also test the target, warn if not empty
- extension: cleanup-space-final-image: do NOT clean apt stuff. done in core now
- the metric shit-ton of debugs added should help the next person who faces this in the future
