Ensure Linux MFSes provide necessary `/dev/disk/by-X` symlinks
As discussed in #233 (comment 37815), we need to extend our Linux MFS mdev
-based environment to support the classic Recovery MFS use case: reinstall a borked bootloader via chroot to host. This used to work fine, but modern grubs need additional dynamically-generated symlinks in /dev. To quote from the linked comment: "our recovery MFS chroot-and-reinstall-bootloader no longer works on Ubuntu 22. The package postinst and/or bootloader install scripts now require the /dev/disk/by-* symlinks, and we save space in the MFS by using busybox mdev."