SW: ship fwupd with fwupd-signed + policykit-1 + udisks2 for firmware updates

SW: ship fwupd with fwupd-signed + policykit-1 + udisks2 for firmware updates

Inspired by Holger Levsen's http://layer-acht.org/thinking/blog/20230514-fwupd/
(currently unavailable, instead see e.g.
https://web.archive.org/web/20230601042943/http://layer-acht.org/thinking/blog/20230514-fwupd/),
quoting from there:

| boot into Grml.
| mkdir /efi ; mount /boot/efi to /efi or set OverrideESPMountPoint=/boot/efi/EFI if you mount to the usual path.
| apt update ; apt install fwupd fwupd-amd64-signed udisks2 policykit-1
| fwupdmgr get-devices
| fwupdmgr refresh
| fwupdmgr get-updates
| fwupdmgr update

Installing fwupd + fwupd-signed adds 19.2 MB of additional disk
space on grml64-full. Without policykit-1 a warning messages appears,
so provide it as well (adding 161 kB of disk space).

Also ship udisks2 (adding 6.512 kB of disk space) for its plugin for fwupd
(also see https://bugs.debian.org/970054). But also its `udisksctl info -b
/dev/...` as well as `udiskctl power-off -b /dev/sdX` (see
https://github.com/grml/grml/issues/198) tend to be useful.