Upgrade to Debian 12 (Bookworm)

[0rax]

This PR should bring BerryOS up to par with RaspiOS 2024.03.15:

• Update BerryOS to be based on Debian 12 Bookworm
• Use new kernel releases by the Raspberry Pi foundation
• Add support for the Raspberry Pi 5 (linux-image-rpi-2712)
• Add raspberrypi-sys-mods package to handle partition resizing and some system tweaks
• Add custom firstboot script (based on https://github.com/RPi-Distro/raspberrypi-sys-mods/tree/b8daae4272db5621ff2c8b2cb8f116711a7bfee4/initramfs-tools)

The addition of the custom init script comes from the fact that the raspi-config resize script no longer works with the new boot partition layout introduced in RaspiOS when it upgraded to Bookworm. This was required to remove support for config.toml and firstrun.sh handling in BerryOS as they would clash with our cloud-init based provisioning mechanism thus we couldn't use the raspberrypi-sys-mods implement directly.

Adding the raspberrypi-sys-mods package to handle partition resizing and being able to enjoy the tweaks present there was not an easy choice (see #5) and some modifications to the files installed by it have been made to better suit our need (mainly removing the /etc/sudoers.d/010_pi-nopasswd file as this conflicts with how we are provisioning our users). But the package has been cleaned-up quite a bit since then and those small tweaks plus the addition of our creating our own firstboot script seems like a good solution now.