[bug#55343] Add support for 32bit UEFI

[Mathieu Othacehe]

Hey,

This seems good to me! There are two things that we could maybe improve
before pushing or later on:

- We could tweak the "grub" package so that the x86_64-linux package
  contains the i386-efi and x86_64-efi modules. That's the
  case for the Archlinux package for instance:
  https://archlinux.org/packages/core/x86_64/grub/.

  This way we could get rid of the grub-efi32 package and rely only on
  the grub-efi package. We would need to come up with something
  similar for the aarch64-linux Grub package I guess.

- The install-grub-efi, install-grub-efi-removable and
  install-grub-efi32 procedures share some bits. It could be nice to
  factorize them if possible.

As everything else is ready to go, I'm fine to proceed here anyway.

WDYT?

Thanks,

Mathieu