conversions were done using https://github.com/pennae/nix-doc-munge
using (probably) rev f34e145 running
nix-doc-munge nixos/**/*.nix
nix-doc-munge --import nixos/**/*.nix
the tool ensures that only changes that could affect the generated
manual *but don't* are committed, other changes require manual review
and are discarded.
This should barely increase the size of the initrd, because these are all symlinks.
With this, systems with dm-cache/lvmcache can also be booted, although the kernel modules for the relevant dm targets still need to be added to the initrd with boot.initrd.kernelModules.