feat: restore extra packages

[gsanchietti]

After an image upgrade, try to restore extra installed packages

Implementation details:

• add a new binary and uci default only inside the image
• start a task in background that tries to reinstall previously installed packages: the script logs what it does and terminates after 5 minutes if the WAN was not ready

[Tbaile]

On the contrary of what we expected, seems that opkg successfully removes the uninstalled packages, I've tried:

root@NSEC-DEV:~# sysupgrade -k -b - | tar -O -z -x -f - etc/backup/installed_packages.txt | awk -e '/\s(overlay|unknown)$/{print $1}'
root@NSEC-DEV:~# opkg install etherwake
Installing etherwake (1.09-r5) to root...
Downloading https://updates.nethsecurity.nethserver.org/dev/8.7.2-dev+20d7224b5.20260310100353/packages/x86_64/packages/etherwake_1.09-r5_x86_64.ipk
Configuring etherwake.
root@NSEC-DEV:~# sysupgrade -k -b - | tar -O -z -x -f - etc/backup/installed_packages.txt | awk -e '/\s(overlay|unknown)$/{print $1}'
etherwake
root@NSEC-DEV:~# opkg remove etherwake
Removing package etherwake from root...
root@NSEC-DEV:~# sysupgrade -k -b - | tar -O -z -x -f - etc/backup/installed_packages.txt | awk -e '/\s(overlay|unknown)$/{print $1}'
root@NSEC-DEV:~#

Green lightning this PR, will try myself.

Source of the command: https://openwrt.org/docs/guide-user/installation/sysupgrade.packages#sysupgrade