Merge tag 'efi-next-20231217' of https://source.denx.de/u-boot/custodians/u-boot-efi into next

Pull request for efi-next-20231217

Documentation:

* replace MD5 and SHA1 by SHA256 in examples

UEFI:

* Refactor boot manager and bootefi command to let the EFI boot method work
  without shell.