feat: actually make use of swap partition

[nis65]

Description

While attempting to test the hibernate feature on my potos based client, I discovered that while the configured swap partition was created, there was no entry in /target/etc/fstab for it.

Instead curtin decided to create a 4GiB swap file instead:

start: cmd-install/stage-curthooks/builtin/cmd-curthooks/setting-up-swap: setting up swap
Running command ['findmnt', '--noheading', '--target', '/target/', '-o', 'FSTYPE'] with allowed return codes [0] (capture=True)
Running command ['sh', '-c', 'rm -f "$1" && umask 0066 && truncate -s 0 "$1" && { chattr +C "$1" || true; } && fallocate -l "${2}M" "$1" && mkswap "$1" || { r=$?; rm -f "$1"; exit $r; }', 'setup_swap', '/target//swap.img', '4096'] with allowed return codes [0] (capture=False)
chattr: Operation not supported while setting flags on /target//swap.img
Setting up swapspace version 1, size = 4 GiB (4294963200 bytes)
no label, UUID=6ed52ac8-827a-4eb9-94c2-050df54c1db5
creating swapfile '/swap.img' of 4096MB took 0.029 seconds
finish: cmd-install/stage-curthooks/builtin/cmd-curthooks/setting-up-swap: SUCCESS: setting up swap

This fix makes curtin to do the right thing, my fstab had this line after an install:

admin@mlc0:~$ grep swap /etc/fstab
/dev/disk/by-id/dm-uuid-LVM-l9zKG2KJEspwAVMhGgPz3NJkWOjg8eUYreDc6dHxBzMN5rBJSGjLbCmZuC1xUbqm none swap sw 0 0

Dependencies

none (yet).

[nis65]

As an add on: I just discovered that having a working (and big enough) swap partition (and pm-utils installed) is enough to make systemctl hibernate work and to wake up in ubuntu 2204. Neither config in /etc/initramfs-tools/conf.d/resume.conf nor a kernel command line argument required any more.