Add support for grub2-bls

[xusism]

Is your feature request related to a problem? Please describe.
Yes, it's because of an exception "error" in the function KRNL-5830:2. The message says "Can not find any vmlinuz or kernel files in /boot, which is unexpected". This started happening after I migrated from grub2-efi to grub2-bls (openSUSE Tumbleweed) and I think its behaviour with the boot partition is pretty different because grub2-bls is more similar to systemd-boot, complying with the BLS standards: https://news.opensuse.org/2024/10/08/grub2-bls/

Describe the solution you'd like
I'm no expert on this matter but I would say probably lynis should at least recognize grub2-bls and understand how it works with /boot partition. I think it does not need kernel files to be located at the ESP partition.

Required changes
Include support/recognition for grub2-bls.

[rootinchase]

Gentoo Linux is also able to support BLS configurations. I have UKI setup which combine the kernel, initramfs, and boot config into a file, that can be signed for secure boot. The files are being laid out according to BLS type 2. When I attempted to copy the UKIs over to /boot, they were still not detected.

My /boot

computer /home/user # tree /boot/
/boot/
├── amd-uc.img
└── efi
    └── EFI
        └── Linux
            ├── 346efcd90ea1dd0738a04b1368e5e631-6.16.11-gentoo-1.1.efi
            ├── 346efcd90ea1dd0738a04b1368e5e631-6.16.11-gentoo-1.2.efi
            └──346efcd90ea1dd0738a04b1368e5e631-6.16.11-gentoo-1.3.efi```