Set EFIvars after talos install

[frezbo]

Feature Request

Set EFI vars to denote the EFI to use sd-boot after talos install is done

We need to write the BootOrder EFI var and set to sd-boot path

Using <boot>/EFI/BOOT/BOOTX64.EFI should in theory should be only used for booting from readonly media (we would still need it for metal image and iso, since we don't have access to efivar store when creating them)

Check the Fallback path' UEFI native boot entries section in https://www.happyassassin.net/posts/2014/01/25/uefi-boot-how-does-that-actually-work-then/