whatever was done to split up the nerdfonts package, the individual
parts now don't work if put in home manager's package set ..

not sure how permanent this will be, but for now it allows me to do some
things that would otherwise be hard.

also element has now bundled in the matrix-react-sdk, so some paths
inside it have changed.

this does a lot of things, most of which are maintenance:
 - sources update
 - adjust newly-renamed options
 - swap some packages that were removed / renamed
 - update nomsring to newer default ghc
 - remove the deprecated lib.mdDoc from modules/*.nix
 - disable the nixpkgs mollysocket module so my own keeps evaluating
 - bundle the package definition of hikari & wlroots 0.15, which nixpkgs
   has removed as unmaintained (in fairness, they are unmaintained)

since nixos-rebuild does not support applying a built config (i.e. one
on which eval-config has already been called) without flakes.

I might or might not extend this into a more proper reimplementation of
nixos-rebuild.